I've used Fasthosts for perhaps 2 decades and it's a tenner a year. You want a domain provider which does catch-all forwarding which effectively gives you an infinite number of email addresses.
Cheers.
I'll hold my hand up and admit it's not something I'd given any thought to prior to ditching BT. I'd never looked into it, assuming it was something that cost a fair few quid and came packaged with other services, so never bothered to look.
I assume you choose a domain name for however long suits your needs, then associate their email package with it and forward your mail on to wherever suits. so you end up with [email protected]...B,C,[email protected]. Though on the site above it looks like for the cheapest package you are limited to 2 email addresses.