Purchase the max of 24,000 miles (£288) and then you have 49k Then stay in a hotel to get an extra 1k.. Here are some good ways to get a great exprience from your 50k:

UK-North America/Central America
out in F class for 31,250 miles + £175
Back in C class for 18,750 miles £105

UK-South America or South Africa
out in F class for 31,250 miles + £212.50
Back in C class for 18,750 miles + £127.50

UK-Central Asia (India etc.)
F class both ways for 50,000 miles + £350

Europe 2 (Spain/Italy/Scandinavia)-North Asia (China, Korea, Japan etc.)
out in F class for 31,250 miles + £212.50
Back in C class for 18,750 miles + £127.50


I only offer these because I am personally an F class nut and in your case it would only cost a tiny bit more and still be able to travel great distances!