I was in a similar situation late last year but with RP3 (c2006 I think, never had full service!). Bought a reconditioned CTD-Adj SV directly from Mojo (2015, I.e. same year) for £145 and it’s better than I remember the RP3 ever being.
Anyway, the point of my post is that these shocks can be rebuilt yourself with care and research. You can buy full seal kits (containing off the shelf industrial seals of the appropriate size) and get a nitro charge from a local suspension service centre. You’ll need to fettle your own hex tool for tightening the new rubber puck/sealer though, at least.
This is what I am gradually doing with my Rp3. I bought the seals from eBay. There are several threads on mtbr and hucking kitty (I think) with diagrams and IFP settings.
Take care if you go this route and obviously only try it on an old shock- if you damage anything other than seals then it’s not an economical repair.