I know you are in Scotland but this link mentions at least one of the common part numbers used for this product.
https://www.fcpeuro.com/products/aud...ring-068130219
"Details
SKU:
ELR-086843
FCP Euro ID:
581064
OE Numbers
068130219, 068198999D
MFG Numbers
086843"
This one is a UK link but I `m sure you`ll find several companies selling this.. vw diesels were a very common thing in Europe... vw jettas, golf, passats, even older audis, LTs, etc are still around... Cars used this exact part up until 1997 or even later.
https://www.ebay.co.uk/itm/161791431316
I always buy much more than six because it is often the case that a certain injector needs to come out for whatever reason. It is suggested to not reinstall them for a 2nd time (the heat shields). Also, it`s a cheap part even when you have 6 injectors under your hood
(The FCP source still seems reliably available ever since I got my 30pieces a few years ago... price went up 69% but $1.69 is still cheap )
For the pump timing you can go around not having the factory volvo tool, you can use the vw diesel timing kit with a little creativity and by carefully removing the d24t vacuum pump to have better access with the shorter tool. Any dial gauge that measures till 1mm will work fine with the vw diesel IP timing tool set. Some owners successfully used gauges that only go up until 0.5mm but that can be very confusing when your desired setting is somewhere between 0.83-0.95
For the injector cleaning/check-up service, it is highly suggested to create a
surgically clean environment otherwise particles may end up disturbing the internals of the injection pump, potentially causing more `trouble` than what you had earlier. Happy to see your project here if you post pictures in the future.