IG provide ISA, Stockbroking and spreadbetting accounts. They can facilitate an SIPP through a third party.
They have a useful APP for trading on the move.
You can hold cash in foreign currency with the stockbroking account to avoid excess FX fees.
I find that their alerts for stocks are flexible and usefull i.e you can set an alert when the 3 crosses the 8 MA of price.
Recently however they are let down in my opinion on the poor customer service. When the site goes down they don’t answer the phone and the chat help does not work. They seem to think that a customer forum is an acceptable substitute for customer service.