Base light has been flashing green all day and all the 'self service' cures have failed. The service status website said engineers were in the area earlier in the day but that there are no problems now. Clearly there are problems still. In SW18 Earlsfield for reference. Getting very bored waiting in the queue on the virgin help line.
It actually resolved itself about 24 hours later so cancelled the engineer appointment. Has been my first issue in over a year so in terms of reliability it's pretty good but the fact nobody really could identify the fault and it self cured after a long period is interesting. I even checked all the cables out to the street myself and they were totally fine.
Due to the nature of the technology and the amount of outside factors & variables that can be involve, these things will involve some trial & error before an issue is identified. Apologies for any inconvenience & frustration caused though. If you encounter any further issues please don't hesitate to get back in touch.