Epson Workforce WF 7610 toner question

Hi.

I recently picked up an Epson Workforce 7610, second hand.

I wasted something with an A3 scanner, which works fine, but as soon as I switch the unit on, it throws up a toner alert.

I think this probably has something to do with the cartridges not being genuine Epson inks. We have another printer, A4, but seeing as this new one is huge, I'd really like it to be the only printer we have.

So my question is, given we only ever (ever) print postage labels and stuff in black & white, is there a way to replace only the black ink with a proper Epson cartridge, and somehow set the printer to print in black/greyscale only (so it ignores the other unbranded toners - or I could even remove them?).

Full branded ink sets are costly, and would be 75% redundant. Failing that, can anyone suggest somewhere in the UK that sells good quality, cheaper non-oem inks for this specific model, that they're tried & tested?

Thanks.