I use iZettle and they are pretty good.
Payments take 7 days to hit your account (they have been quicker, but never slower)
2.75% fee and no other fees to pay. (If you don’t use it you pay nothing)
The Chip and Signature reader isn’t really as good, you need the customer to have an Internet smartphone to process VISA credit/debit cards and its a bit of a faff to be honest.
I got the Bluetooth Chip and PIN machine and it is far better but it costs £50 to get that one (worth it)
You can email a receipt straight away if required which is good for me as it saves on paperwork for corporate clients.