If you look in the one world forum there should be an up to date price workbook which will tell you where is the cheapest places to purchase.

If you don't want to start miles away I have found GIB and ARN to be cheaper in the last few years.

There are a few different types of fares you could look at, some based on mileage rather than number of sectors.

Also if you start somewhere other than the UK you could fly your trip, have a break in the UK for some months and then have another holiday in the middle east later. This is what I've done twice. For some reason they include the middle east as part of Europe.

But you'll get loads of advice in the one world forum.