[Georgeandkira]

Just a 'chime in' from the other side.
For the effort and time it'd take to find INA pullies and whatever brand water pumps, one might as well go with a genuine parts kit from a REPUTABLE parts source online or (gasp) the dealership.
I'm not sure how the conversation would go in the UK but I'd just politely ask 'em for whatever discount they have.

For reference, go to eeuroparts.com and fcpeuroparts.com (both in the US) just to see the kits they have. I don't know any of your sources or shipping over salt water. IPDUSA.com is another honest source but for other Volvo stuff.

Note: I bought a "Gates Kit" from a 'reputable enough' firm. My timing kit was sent out by disreputable 'drop shop'. Many sellers routinely have orders shipped from many different warehouses. The belt looked good but my Gates tensioner was frozen solid, the idler looked cheap and it was all in a tray covered in ripped cellophane which was from something else entirely.
The 'reputable enough' firm made good on a refund quickly.