Scooberlicious

I have just bought an Imported Subaru, its a bug eye model Year 2000
Its an Sti v7.
n/s rear is knocking over bumps, bigger the bump, louder the noise. I think the strut has gone? but i cant tell? Nothing seems to be loose?
Is there anywhere i can take it local to Slough to get it checked out without paying an extortionate amount?
It has red struts/shock absorbers with coil over springs, the labels on the struts have the following code;
20360FE000
FB70
YARH

If the Strut/shock absorber has gone, what is the best recommended replacement according to the set up i already have, should i change the whole system if i cant find a replacement or should i change just the rear two shocks? If i can find a replacement where can i get it from?

Also what is compatible with my subaru? Cheers

Ok just Googled the part number, and have read previous threads.....common problem on Sti's .
I need a whole new set! cant be bothered to exchange for a replacement as it just re-occurs.
Any body got a decent set of secondhand shocks? PM me please.