The only Other thing they could do is maybe have a big pool to be used if a pipe gets blocked.
The pool start to fill and (all things being good) the blockage is fixed before the pool is full.
Then, when things are working, the pool is emptied.
But that would require the pipes to take even bigger loads.
They have several - the Thames and peoples houses! 
I love the way they have used traditional Imperial units of measure - the tunnel is 3 london busses wide. Missed out on telling us how many Nelson's Columns it is deep though.
I love how offtopic this thread is getting! Norway was my first choice until... Russia. Far too close for my comfort. I put "not being close to a nuclear attack" slightly further up in my hierarchy of needs compared with "having sewage systems that work well" 
Yeah, ok... 
I kinda walked into that - didn't I?
... no, no, you don't get me to start down that topic as well! ...
Having recently been to the Baltic countries and Finland.
I think they all live in the sunlit uplands so you'll be pumping uphill.
I have one question for you:
Do you have an extra sump pump ready for that day when your sump pump fails?
This is a good investment (I know from experience). Also the day it fails, others will most likely be looking for a new pump too.
The only EXTRA to that is also make sure you have a good place into which to pump that is well clear of your place.
And respectfully away from anyone else's.
The pumps inside the sumps are all dual redundant. Every 6 months you are supposed to check both sumps are operational and clean the sumps out. Worked very well so far. The sump pumps are not bombproof, but they really are very good. To give you an idea, I have 2 or 3 cheap pumps (Ā£40-50 each) which I use for "general purpose" stuff, i.e. for emergency, not physically installed into the sumps. But these sump pumps which are "permanently" installed are about Ā£1400 for the pair including the sump itself, so yeh - the budget goes towards design quality / resilience. They have dedicated cable routes underground for incoming mains, connection points that are above the flood level (well, according to regs anyway. The actual situation is more dicey), and other aspects of system design that have already been thought through by others.
To answer your question more closely, yes I have a range of pumps. In total I counted 9. It's ridiculous. 2 sumps, each with 2 pumps (permanent), plus a foul sump with its own special pump. That's 5. Then we have a puddle pump for hot tub emptying which can be deployed as well. Then I have 2 "semi" permanently installed pumps in 2 sewage manholes which I haven't even mentioned on this thread yet, plus I have what I call a "roving" pump which I keep in storage. That last one is so powerful. When the hose popped off, the water geysered into my face and almost knocked me out, then it flew up I'd say about 4 metres into the air (I was outside just by the front of the house). It was at this point 4am / soaked head to toe in foul water and stressed about floods, looking back, that I start to think I should move to another country / question life choices etc.
As well as the "building regulation" requirement sumps and pumps, I also have these two dodgy DIY pumps that go into sewage manholes, for this backwash scenario. I should never have to put these in, but for the faults in our sewage network causing the back surge. I have plumbed in some high pressure pipes inside the basement, they go through the walls and outside, then they periscope up and point out towards the street. It is not legal to pump water onto the street here, certainly not dirty / foul water. On the other hand it's not legal for the wastewater company to allow sewage into my home, and the inspector understands the situation hence I don't mind writing it down here. This touches on @Trying_to_learn's point about "venting out into the street"... I didn't mention before but I have my own special DIY system that essentially does just that. Part of it is permanently installed, but I still need to be physically present to ensure it all works properly and also last night I connected an extension pipe onto my periscope so the water got further away from the house.
It's complex isn't it?
Well, while Yorkshire Water isn't a lot better than Thames, I can say that the quality of life here "up North" is much higher! 
Just like another country - quite literally actually. And Sheffield in particular has the advantage that much of it is WELL above both water tables and rising sea-levels, something that certainly cannot be said about London.
#offtopic
This thread could get dangerous for me, my other half lived near Haworth growing up, and I have a very soft spot for Hebden Bridge to the point where I've given thought to giving everything up and moving up there. I may end up doing that. We have put what feels like a lifetime of blood sweat and tears into our home here in London which is the main thing keeping me here right now (well, kid school and being near elderly mum, but those are not insurmountable...) Today is definitely a day of reflecting on life choices for me.
I do hope you have managed well with the fundamentals, cleaning the mess I understand, hope it moves in the right direction
Let's keep us updated about the other part when you start implementing, it will be so interesting to follow (different to what you just done, a bit "white collar" work at the keyboard instead)
Yeah the problem is that the UK decided about 20 years ago to start outsourcing the management of their water supply and sewerage systems and the companies that took the contracts have done very little preventative maintenance etc
It is at a much higher level than the local council (and is a political hot potato in the UK) and is another one of the things that is being brought to the fore by the extremes of climate change.
Craig
I hope the recent change in government may help this situation.
But with all the stuff that needs doing, I fear is may take a while.
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