this is a trip that will run over two days, outbound early Saturday morning, returning the following day. There is a reason for this specific trip, that being a mate’s stag weekend.
Guaranteed to be cr*p weather then, at Newcastle, or Newquay or en-route. Or probably all 3. This is the UK, after all!
Plan B is... car? train?, bus?... Or miss the event?
Don't let the requirement to get there for a specific day and time "cloud" your judgement regarding the WX.
FBW