Buying house with structural changes: what to look out for?

I'm in the process of buying a house, and the vendors have made some structural changes to the property since it was built 4 years ago:
- some internal walls have been moved to change the room configuration upstairs;
- the bathroom has been extended into part of another room, and the window that was part of that room has been replaced by a smaller window to match the existing bathroom window, meaning that the walls (internal and external) had to be built up around this smaller window;
- a velux window has been put into the sloping roof at the front of the house.

What should my solicitor and engineer be looking out for (certs of compliance, etc.?) The house is timber frame.

Thanks!

(...and apologies for the accidental double-post in the Don't Ask forum . In my defence, I plead Miserable Wet Monday Syndrome!)

Make sure planning permission was sought and granted for the changes.....

These changes sound reasonable enough (the fact that one window was changed to match another suggests a careful owner) and it would be normal for your structural surveyor to examine these (but by all means point them out to him/her and ask for his/her thoughts).

A velux window to the front of a house normally requires permission as far as I know so you'd want to check on this.

Thanks for the replies. I'm all new to this house buying process and every step seems to throw up something different, so the advice is much appreciated.