Fantastic that you don't have to live in it yet! (There's a wreck for sale just opposite our house and we would love to buy it and renovate it..but just can't face living in another one, and can't afford to run 2 houses).
Worst thing is the amazing dust you get from 1) ceilings coming down - loads of gross thick black muck, and 2) anglegrinding (cutting through plaster) for any reason - e.g. putting in channels for cables.
We spent a long time planning what we wanted, drew out rooms to scale and made paper furniture to scale, then moved it around, checking for number of electrical sockets, length of radiator (we replaced some single radiators with shorter double radiators to give us more wall space), how doors on furniture or in kitchen would open, etc. The planning is very important. Once you know what you want where you need to make sure you can both communicate well with, and trust, your builder - we had a few quotes which were cheaper but the builder didn't want to do it the way we wanted but by a cheaper or easier way (eg. wanted to put in a saniflo loo in downstairs WC, but we wanted to pay more and get a proper plumbed in one)..wait until you find a builder that is on your wave length! (took us 9 months and although we still had some problems, most things were smooth). When we had big jobs to do eg. creating our utility room involved knocking down a downstairs bathroom, putting in new windows and patio doors and building new partition wall, plus new boiler, and changes to the lighting circuit, we employed a project manager/builder - he was able to keep the work flowing and got all the different tradesmen in at the right times...for other, more bitty things, dh did it himself (he can do carpentry and plumbing, and does electrics but we get an electrician to check them and sign them off - he can't plaster large areas (yet :) ) and we saved up all the plastering until we had enough for a plasterer to do in one day - saves a lot of money.
Since we lived in our house we had to phase the work, phase 1 was the bedrooms (we all slept in loft room then), phase 2 was the utility and kitchen (we created a kitchen area in one of the receptions and the kids got their own bedroom at last), phase 3 was the reception rooms and downstairs loo (we moved into one of the bedrooms and lived upstairs for a year), we have now got use of kitchen and receptions and all but one bedroom, just need to finish off downstairs wc and re-wire remaining bedroom..then re-carpet because there is ingrained unshiftable dirt in most carpetted areas....and then we start on the garden :o
I was 5 months pg with dd when this began, and she is now 2 and a half yrs, we also have an older ds who is very knowledgable about building work now.
At times it has been terribly depressing, and felt that it would never end, also was worrying 'destroying' what was our biggest asset (dh was made redundant at one point and we couldn't have sold the house in the state it was in), but it has been worth it in the end. Good luck.
If you decide to go for it and need someone to whinge about the dust to, I'm here!