Another vote for Largo. Our buying group has an account. Store man has an encyclopaedic brain.
Try Largo plant in Norfolk. Always use them and find them excellent and very helpful.
I happily use after market filters as long as I know of them. Will be visiting Largo plant in a week or two for a selection of filters and to listen to the store and sense of humour.
Ive never had anything but great service, help and advice from largo. And they don’t know me from Adam.