The Night QUALIFICATION (not rating) can be done as part of your 45 hours of PPL training. Just make sure you meet the NQ requirements (solo circuits and nav with instuctor) and log it correctly. You then have it issued on your PPL. It is not a rating, therefore the hours CAN count for both. Some schools do not like this as they miss out on an extra £700 after your PPL. Do not be told otherwise. You can do it.
IMC IS a rating, so has to be done seperately. However, you do NOT need an IMC to get your ATPL. You need an IR. In fact, it was designed for those who like to fly PPL in marginal wx but did not want an IR. A handfull of people like to get it as they say it helps you with the IR later down the line. However, most don't have a spare £4000 knocking around to get somthing they just don't need.
To summarise, in theory, you don't need to budget for either.
It's not often you get good news like that in aviation. Trust me.
EK