Some family are planning to fly into T3 from DEN on BA218 in J, then onto a domestic connection from T5. I'm not sure what advice to give them re: the most painless yet best way to make this connection. They travel infrequently and have never done a connection like this before, so I want to keep it as simple as possible but at the same time direct them towards the best possible experience at LHR.

Am I right in assuming they will have access to the arrivals lounge at T5 if they take the airside bus from T3 but then exit landside at T5? I know this is usually the recommended route at T5 anyway to avoid flight connections when it's busy.

They have a very long connection at T5 so I'm thinking of advising them to go landside and use the arrivals lounge before going back through to departures. Will they have access to fast track security when re-entering? They have no BA status but I'm assuming they should get Business UK boarding passes as they will arrive from DEN in Club World?

Thanks as usual for any advice.