I’d stay in NI. You couldn’t buy our house for that, but we have a large 5 bed (we’re a large family) in a very sought after area. We could have spent £200k less if we’d only needed a 4 bed, been prepared to go a little further out of town/away from the beach (5min car journey rather than 5min walk) or if we’d gone to a cheaper part of the country.
The big advantage of NI is no school zones. We have excellent schools both at primary and post-primary level. Many of our grammars are outstanding (not just academically but in terms of resources and facilities - they are on a par with private schools in mainland UK), and the vast majority of our non-selective post primaries are excellent too. Because we don’t have school zones you can choose the area to live in that works for you, and still choose the right school and have the same chance as anyone else at getting in.