The US has dedicated jamming aircraft, but, as I understand it, this is not a capability the UK possesses. I believe it is a potential weak-point across most European defences.
An attraction of F35 to the UK would be if it could act independently of such support, as we are struggling to afford carriers and strike aircraft, before we get to things like AEW and jamming platforms. If F35's Day 1 capability depends upon dedicated jamming support, it is difficult to see when the UK would be able to operate F35 independently of the US in a sophisticated IADS environment, at least until we could afford our own capability - which looks a very long way off at present.
Or have I got my facts wrong here?