Thanks General Maximus. I checked the speed upgrade again today at
http://keepup.virginmedia.com/speedupgrade and it now states by end of March 2015 and that's just to tell me when the upgrade will be ready! So called Retentions as you advised, complained (again!), and they simply did the 50mb upgrade there & then and took the princely sum of .64 pence off my bill! why couldn't CS do that when I spoke to them last week?
I did have to renew for 12 months as you said.