To All
this thread has been updated, with some useful info, for those suffering too.
XP VM suddenly slow, Win 7 fine
The problem I had was, nothing showed up using TaskManager, but it was pretty obvious something was interfering with the XP VMs.
The biggest pointer to some sort of issue, besides everything taking ages, was the lack of and System Process Idle time it was always 0%!
Tracking down what was the hard part, luckily to link above mentioned AVast, and I discovered AVG has done something similar.
Thanks for all the comments and help