I recently bought a 'v-cutter' for my PPP, it is a good alternative to a blade for the UK.
I was annoyed at the high price I paid 'heinnie haynes' for it though. Their service is 1st class albeit a little pricey. So after trawling the web I have come across this store who seem to sell the v-cutter £2 cheaper (20%). If anyone else finds any UK sources of SOG spares, please let me know.
Disclaimer: I am in no way associated with this web retailer. I have never ordered from them before and cannot comment on their quality of service. I merely though it was worth mentioning.
http://www.bronzemoonoutdoors.co.uk/sog-v-cutter-powerlock-stainless-finish