@Stupified
Personally I'd have preferred her just to ask rather than drop hints, I hate that!!
My main issue here though is YOUR relationship. Are you happy? Do you see a future with DP? If so, how to do intend to secure your house in Wales? He appears to have developed a 'we' attitude to it?! Did he put time & money into the renovation? Does he see it as a joint property?
I know, especially when you each have kids settled into schools/activities/other parents, it's not always practical to live together, but you need to be careful how much if you 'life/money/future' YOU are putting into the relationship, compared to him.
He'd rather make you seem unreasonable, than upset his ex wife by saying 'no, that's not appropriate. It's not my house anyway, it's OP's'. Blue print for future behaviour!!
As for the 'Wales house'. It also sounds like his kids see it as a joint house, not yours, why is that??
If the 7yo said about mummy taking them, I think that's just 7yo normal! Your DP should have said 'No that's OP's house, it's lovely we all get to go, but only when OP is going too' or whatever, but closed it down.
As for me, it would depend which ExW we're talking about!! Some yeah, no problem, some only if I was putting down fresh footings! But YOU are not terrible saying 'no'