Just remember that the MEP can only be done in the A/C, if you would want to renew that as well.
A few years ago I got stuck and used an examiner from one the the big schools as the one I had organised privately went tech.
They charged me 180 pounds examiner's fee, which is the going rate, PLUS 2 times 100 pounds being the hourly rate for 'advanced instruction', so 380 pounds examiner fee!
Cheapest way to do it is organise an aircraft outside the approved FTOs and find your own examiner. Assuming you can go straight into test (no training required) a MEP/IR renewal on an aircraft shouldn't be much more than 600-700 pounds in total. You might have to do without HSI and RMI though.
Regards
Gerard