check via double speed checker if in your area are going some work
(example your speed is due to may-june)
http://doublespeed.virginmedia.com/
If is going work now then you may have these problems until they finish (had almost same issues with frequent disconnections)
If not going any work (according to double speed checker) then VM has a fault somewhere or if you have disconnections Only after R36 firmware you need to report at VM forums because i have seen few other complaining about disconnections after the R36 upgrade
As advised call them again ( i know is annoying) because at VM forums you will wait few days for official reply