Last time I was in London (early March, though many years ago) it was pretty bloody miserable too, but it seemed to be doing well enough despite that!
If any given day being well be suitable for hanging out at the beach is a gamble that would seem like an argument for choosing to live near it, where you can easily make spontaneous trips when the weather suits.
FWIW our most recent mini trip away was to a coastal town in Victoria in the middle of winter, where the weather was never going to be beach-suitable, other than for the dog (who loved it of course). And of course the die-hard surfers. But it was still a very pleasant getaway, with plenty to do and see, and several places we visited were booked out.
Other than last year, I can't remember a year in the last 2 decades where going to the coast wasn't such a massive gamble.
Even I have given up and decided to spend a week in Turkey.