Apologies, I didn’t see your responses until now.
I don’t know if you can self install the Liberty Shield settings on any router, but to be honest, at £20 it wasn’t a deal-breaker cost. They have admin rights over it, so can make adjustments at their end if necessary. The odd time that has been required, provided it’s between 9-21:00, UK time, it is done in moments.
They seem to have plenty staff but my experience, over more than 10 years, is that they seem to try to allocate the same person for consistency. That said, anyone I have dealt with has been very competent.