merging 2 bathrooms - effect on value?

Perhaps not the correct location as it falls somewhere between home improvements and house values but anyway.

We have a 4 bed semi-d bought 2nd hand off the previous owners. As they bought the house new, they laid out the house themselves and the size of the main bathroom upstairs (1.7m sq) is far too small.

There is also an ensuite which backs onto the main bathroom which is too small and we don't use (2m X .7m roughly) with wc, shower and mini basin.

We've more or less decided to take down the partition wall and merge the 2 into 1 decent sized bathroom, which won't even be huge afterwards.

However I'm concerned that a 4 bed semi d without an ensuite (even though its so small its useless), will be a problem when we come to sell probably in 5-7 years time. The house location is excellent in a mature area.

How much of a turn off will no ensuite be in comparison to a well spec'd main bathroom? House size overall is about 1200sq ft.

There is another decent wc downstairs at the rear of the house (not under the stairs).

An ensuite does add value, generally, but once you have a guest WC as well I think you're better having one decent sized bathroom than two painfully small ones. The ensuite sounds virtually unusable to me - barely over two feet wide? You'll have buyers who can't even get in to it! And if you're looking at being there for the medium term, I reckon you should do what makes the house work for you, rather than retaining an ensuite you don't use for a very marginal possible return.