I'm going round and round in circles, and just wonder whether any of you good people might have any information, ideas or opinions that might help me make some decisions...

I found a house I liked - not perfect, but very nice and practical, for £130k. It has a new, good quality kitchen and bathroom, but will need rewiring and a bit of patching up. Unfortunately (a) the vendor isn't ready to move and doesn't want to be hurried, and (b) it's probably only worth £125, and maybe not even quite that, since the local market is stagnant. I offered and was rejected, raised and was rejected again, and we've stalled... So I started looking again.
I'm thinking again about another house I saw last summer, but rejected at the time because it needs so much work. It will need a new kitchen, bathroom, a wall that has been put up in a silly place knocking down again, rewiring, a new gas CH/hot water system, and total redecoration. It's in a better location with a great, open view. It also has new windows and doors, compared with 10-15yo ones on the other house. It's on the market at £120, but has been for almost a year, so could probably be bought for £110-115k.
Both houses are ex-council 3 bed semis with garages, with good gardens, on similar sized patches, in different but nearby villages.
Other similar houses are to be found for around £130-140k, but I haven't seen any I like yet.
The question is, is £15k enough to do the work that the second house will need? I'm estimating costs as follows, with some work done at 'mates rates'...
Bathroom - £2k
Kitchen - £4k
Walls knocking down, possible RSJ and replastering - £4k
New boiler and system - £4k
Redecoration (labour and paint) - £1k
Do these figures sound reasonable? (I'm in Yorkshire btw).
Also, both houses will need rewiring; does anyone know what I should budget for that?
In my dreams, I'd also like a little garden room extension and an basic loft room... What sort of ball park figures should I pencil in?!
The other question, of course, is whether I can face taking on so much work! I don't know the answer to that one yet, so if anyone has any experiences they'd like to share of their own house projects, please do! (I would be able to stay in my current house while work is being done on a new one, for a month or so anyway).
Sorry for such a long post, and thank you if you've read all the way though... I'm a single parent, and need someone to talk all this through with really; but if you lot are happy to help, I might be able to stop my head exploding!