We're booked to travel INV - LHR - CPT in early November, on a 241 redemption. We need to have a negative PCR which is less than 72 hours old at the time we depart the UK, and I'm concerned that the timings make this difficult to arrange. The diagnostic companies I've looked at offer results 24 to 48 hours after receipt of the sample (which we would have to send to the lab by Royal Mail, so that's 24 hours or longer on top). To complicate matters, our Inverness flight departs at 6.50 am, while our Cape Town flight doesn't leave Heathrow until 6.15 pm - but as it's all on one ticket presumably we'll need to provide the results of the PCRs before we can board in Inverness, leaving us with an even smaller window.

What can we do to ensure we have our PCR results in time for our flights?