Rich
I spend a lot of time and expense on this subject over the years,, I can only speak re Volvo, but, even before block exemption,, , it was the customers choice as to where his vehicle was serviced , so long as it was done to manufacturers service specification, with as you say "'suitable quality'" the vehicle would still be covered under the makers standard warranty,
I would always play safe and use "Genuine Branded Parts" The Sport has been serviced "outside" the dealer network, and has been back for warranty items recently, with no problem,
With the RAC Insurance warranty you have,, most used car warranties are the same, they will only pay out, if the item that has "mechanically broken down" is listed in the policy, also they will stipulate the service interval margins, normally 10 days either side of due time,, the fact that window regulators are not a service item, has nothing to do with it,, the policy conditions were broken by late servicing
Like most insurance policies, if they can get out of paying, they will try,, have a case at the moment with a V70 AWD,, the front angle drive stripped the teeth of the pinion,, the warranty firm are claiming the vehicle was drive after the event,,!! like yes,, about 200 yards out of the outside lane, onto the hard shoulder !!