Well your DH is wrong, a place isn't just a place, but I'm wondering if in fact your local area has more possibilities than you think, you just can't see or take advantage of any of it because you're snowed under with FT work and FT childrearing and most of the mental load. And schools an hour away in opposite directions, that's a lot for anyone!
When you say "more things around to do, more places to visit, a wider range of people" well if your kids' needs mean you can't access local kids' activities, then what kind of "things to do/visit" do they enjoy - museums? NT properties? Historic battlefields? RHS gardens? Theme parks? Amazing book group, local library maybe?
If you're in a market town commutable to London, why do you go only every 3 years - is it hard logistically to take the kids? Could you take a day trip into town (alone, with the kids or to meet friends) on one of those flat weekends and feel the energy of the city? I live in Windsor, for instance - I have friends and ex-colleagues who when we worked together commuted in from Newbury, Guildford, Beaconsfield, Basildon, etc. My DH works weekends so sometimes I meet friends on the South Bank and go to the Tate Modern, bimble around Borough market and take the kids for a pizza. The coast I miss too, I grew up on the beach myself and sometimes miss the sea intensely so we try and spend school holiday times near the sea.
If you pretended you were a tourist and put in your town into Tripadvisor, does anything come up that you hadn't thought of? Eg. I just did Newbury and who knew there was a museum of West Berkshire, and a special house open only in February to see a spectacular display of snowdrops - random! www.tripadvisor.co.uk/Tourism-g190745-Newbury_Berkshire_England-Vacations.html