I understand your concern.
Up until a couple of years ago, I never had any regular issues with Virgin and the WCML in general, now every time I'm in London I'm periodically checking National Rail and RTT throughout the day to check if I'm still going to get home...
Yes Avanti a much less reliable service than Virgin. My daughter lives in London and regularly uses West Midlands Trains to Crewe as its far cheaper, more reliable although slower. Pendolino Trains give her motion sickness which the West Midlands trains don't - maybe all the extra stops help too.
I'll be working in London 3 days a week and 2 days at home and they are pretty flexible so hopefully I can work around it as I really don't want to be driving down. The guys from the North I used to work with in London would get up at 02:30am on a Monday Morning for the 3+ Hour Drive so they would miss the traffic. Then on a Friday after an exhausting 50 Hour week would depart tired at midday for what regularly turned into a 5-6 journey home! Give me the train any day - sleep on the way there or back, read a book, watch a film, dink some beer, eat some food.............