We bought a fixer upper last December. It's tough going, and has proven to be a lot more work than expected.
If you buy the house, will you need to move in straight away? That will make a big difference to your decision. We are living in our renovation and it is HARD. The amount of dust from all the work is just insane.
So far, we have replaced our entire central heating system (new boiler, relocated. All new pipework up to modern standards and brand new radiators throughout). We paid for designer radiators so this set us back almost £20k, but would have been almost £15k without them due to the work. This took 3 weeks to complete but may have been quicker if we weren't living there as they had to put floorboards back at the end of each day etc.
We have had the house partially rewired. Sockets were fine, but ceiling lights were unearthed. Not the end of the world, but would prevent any metal light fittings or downlights etc in the future. We also upgraded all our switches and sockets, and added lots more sockets while we were at it. This took 1 week and cost us £4k. We had a new consumer unit also, which cost us £600 IIRC.
On top of this, we have paid £900 to have all the chases in the wall filled, and then an additional £600 to have a ceiling overboarded & skimmed after we discovered potential asbestos. The ceiling had been wallpapered and this was found after removingt the paper. The ceiling had a big hole from when the warm air central heating was removed, so covering the whole thing over was an easier solution.
Bathrooms, Kitchen & Flooring are all on the 'later' list as they are just cosmetic and require more money than we have right now. If I wanted to, I could make reasonably cheap improvements to them but it's not top of the list.
We went into this house with £50k in savings, but the house has eaten it all up in various ways. All that gets us through is the fact that it really will be lovely when it's all finished, and we couldn't afford the size of house we wanted without making a compromise on condition.
Only you can make the decision on whether this house is 'worth' it, but I would say you and your partner (if applicable) need to be on the same page about it.
Also, definite yes for a Level 3 Survey. Ours gave us a heads up about a lot of the issues we have tackled.