Not all vets offer a titre test or are in favour of them, so this is something you may have to hunt about for.
Vaccicheck Titre testing prices vary greatly, so do call around to find a competitive one.
The best price we found locally was £39.98 with a £44 consultation fee at:
Medivet Richmond
Address: 171 Lower Richmond Rd, Mortlake, London
SW14 7HX
Tel: 0208 878 6080
Other Medivets should be around the same price.