Warren, many thanks, looks like its time to buy a fresh batch. 
P.S.  I there  a date  best before or similar on the package, i don't seem to be able to locate one.

We can trace an exact expiry date through the batch number but for this resin it is 6 months from date of manufacture which, due to us having very short turnaround times means you can assume 6 months from ordering.   Also in practice, most resins will, if kept properly, still work after the expiry date but the properties will begin to degrade the older the resin is.  Some resins last a long time (eg most epoxies) and others less - PU's and polyesters for example. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant