Heathrow Trasnfer Advice

January of next year I'll be transitting through LHR and need some advice. Usually we are on VS020 which arrives 11am or UA954 which arrives 7am. This gives lots of time to meet family in London prior to the 6pm departure of VS601, however UA have knocked off the noon flight ex SFO and now it leaves at 7pm. The LHR arrival is 1:25pm, this means no meeting family, which I can live with, or a switch to the SFO-ORD-LHR route (no way am I doing this in winter!), so its the afternoon arrival for us.
Question, normally we would check bags through from SFO-LHR-JHB, then in London, leave the airport, see family and then check in at UC as normal and head to CH.
This time I need to know the best approach to take, once before we followed the in transit option and got stuck in a huge queue, because only BA had priority, I'm thinking it's better to just walk from T1 to T3 and use regular check in proceudres given we're in UC.
Thoughts?
Question, normally we would check bags through from SFO-LHR-JHB, then in London, leave the airport, see family and then check in at UC as normal and head to CH.
This time I need to know the best approach to take, once before we followed the in transit option and got stuck in a huge queue, because only BA had priority, I'm thinking it's better to just walk from T1 to T3 and use regular check in proceudres given we're in UC.
Thoughts?