Flights to Cape Town in Nov/Dec - is this scenerio possible?

I need to fly to Cape Town in November and December however the flights are looking to be quite pricey. Is it possible to do the following for example:

Fly London - Cape Town on the 15th November returning to London on the 31st December.

Fly Cape Town - London on the 25th November returning to Cape Town on the 20th December.

This works out to be about £700 cheaper! Or do you think this will get flagged down?

I will be checking in Luggage both ways.

The flights have increased dramatically over the xmas period compared to to previous years!

Nothing wrong with that at all. Just make sure you take copies of both tickets with you in case you are questioned on the length of stay booked under the first one.

VS and BA are the only non-stop options on the Cape Town route now, so prices will inevitably rise.

Emirates and the middle eastern carriers might be a one-stop option.

Have done this before to HKG and BOS with both BA and Virgin and never been flagged up myself.