I have started a new business and need to do quite a lot of both colour and black and white printing my old HP3050 is eating carts at an alarming rate even getting them refiled at the key cutters its bloody expensive any recommendations for a printer with lower running costs than the old HP would be much appreciated.

Sounds like you need a laser. How much you spend will depend on how much printing you do.

I’m not sure that

wont break the bank

and

need to do quite a lot of both colour and black and white printing

really go together.
The colour printing is going to cost you whichever way you look at it but inkjets are the most spendy as you already know.
I used to run a colour laser but the hidden costs there are the fusers etc.
Thankfully I don’t need to print much now as everything is in PDF format (or similar).
What sort of stuff are you printing?

I have a HP LaserJet Pro 200 colour printer. Network capable. Does colour work perfectly well. 4 carts (non genuine) cost about £80ish.

I also have a basic black and white HP 2015 laser printer. I tend to use this more as my wife reels off lots of worksheets for her teaching and they only need to be black and white. I must have gone through thousands of pages, and only ever changed the toner once for £35 ish. I’d say the mono laser is cheaper than the colour to run for black and white stuff.

You can get refurbished lasers reasonably cheap. My colour laser is a hand me down, and for the sake of set of carts its up and running perfectly.