Hi Bob,
I totally understand what you're trying to say. I am afraid, that as you live outside of the UK we are unable to arrange your visa so we recommend you contact your closest embassy, consulate or high commission for advice.
We would always recommend that your visa is valid for the whole trip - there would be nothing worse than getting in to trouble whilst on holiday. The visa is valid for 3 months from the date it’s applied for, so you could apply for it mid-December if that would be your preferred option. We can't say what Trailfinders process is when it comes to visa's so it might also be worthwhile having a chat with them too.
SarahS - Sorry I did mean "before" your trip.
I hope this helps.
Kindest regards,
Monty