Thank you for reaching out to us in our community and welcome back, I am glad to hear your issue has now been resolved, in regards to credit for this issue this isn't something we do, if you have had a total loss of service over 48 hours our auto compensation will kick in, this doesn't cover intermittent or WIFI issues, you can find out more here.
I guess, I've not really let them corner me in such a way before.
I recently binned there M350 service at my home and stuck with my 50Mb EE connection, wasn't much of a speed issue with Virgin though, was just a disagreement over TV service and when I looked at my needs the backup line (office purposes) was better for certain things and I wasn't using much bandwidth and when I need bandwidth I just let my phone take over as it draws in 300-400mbps.
Unfortunately I only get 30/4 via ADSL on my street which just isn't quick enough for me, esp. as I work from home now post-COVID. Really hoping some other quicker services come out in the area soon as Virgin's CS is abysmal!