How many miles/km have they done and in what conditions out of interest? I’m on SL23 rims and they’ve done 10,000km in largely dry-ish conditions and they’re fine for a good while yet. Everyone is different though and clearly YMMV.
I guess changing rims involves changing spokes too unless you’re lucky on the ERD/flange combo to re-use the spokes but that does sound pricey to me, maybe get another quote for the work? Changing/servicing hub bearings should be in the £50 region I’d have thought IME?
Edit: what’s more, I may be wrong, but I thought that a lot of these UK-supplied wheelset (eg. Hunt, Bax etc) use Novatec/Bitex type hubs… If you are having bearing issues with White hubs then I’m not sure you’re going to fare any better with those? An expert will be along shortly to confirm or refute!