The "mech" itself is usually where you choose the currency.
There are some mechs that can be programmed to accept certain coins, but the cheapest route is to buy a coin mech that is specifically for the coin in question (10p, 20p, etc.) The US mechs can be had for about $13US each, I suspect the UK mechs will be priced similarly. I used token mechs (.25mm) instead.
I know Happ has a UK office, that might be the best place to find a mech for UK coins.
Kevin