Thanks OnePlan. In answer to your question, this is somewhere we're planning on staying 'for life' so with a toddler and another one planned in the very near future we just thought it would be more practical to end-up with a large master with ensuite, good sized second bedroom and two smaller doubles - one each for the children and a guest room. I know it all boils down to individual circumstances, hence the above but it's otherwise a large property (nearly 2000 sq ft) in a lovely plot and area so the only real compromise seems the missing fourth bedroom.

I think if the location works for you and you can afford to extend, and can’t find a better alternative then it make sense to extend. Especially if you’re going to stay for a while! We are nearing the end of quite a big extension/refurb and it has cost a lot, but is cheaper than moving would have been, and we are aiming to stay here for the foreseeable future, so it felt worthwhile spending the money. If you’re extending, moving walls, new bathrooms and kitchens, it will rapidly add up, as you’ll also need new Flooring, extra windows etc Is there enough head height in the loft to do a partial loft conversion perhaps?

Don’t have dimensions but the en suite looks larger than it needs to be. I would move the wall between bedroom and en suite back a few feet then you could have wardrobe storage space along the bedroom side of the new stud wall. As building a new stud wall you could have a pocket door and I would put the bed and bedside tables as in the diagram above facing the window. In the ensuite I would make the shower as wide as possible stretching between the new stud wall and the exterior window wall and put the toilet and basin side-by-side along the window wall

If you intend staying here for a decade then you should make this house work for you and not the next people. I think that since you have already flagged extending in 10 years you should also future proof your plans now. If it were me I would have a bedroom where the current big bathroom is in order to give you the possibility of later extending over the ground floor extension. I would also want a super sized bathroom for my use - I have always believe the person paying the mortgage should have a better bathroom than people who visit three times a year. And I would take the view that when a loft bedroom is later added it won’t matter if one of the four bedrooms is compact. So I offer an alternative.