Cambelt Vs Cambelt Kit
 

I had my belt changed at the weekend, Subaru wanted a small fortune for just changing the belt and so i had a friend do it at his local garage. He suggested that i should go for a kit replacing the whole lot, but it was £300 ish + labour and so i opted just for the belt.

Could this be a bad thing just getting the belt done, he did say the rest was ok but you never can tell, and subaru just wanted to replace the belt only?

Oh forgot to mention, I also had the tensioner replaced - is there only one of these and does this make a difference?

I had mine replaced by RCMS at my 50k service last year. They recommended changing the tensioner as that is hydraulic and was weeping oil. Now this can be 'serviced' by some ppl, but i chose to get a new one.
RCMS also change the other idler roller for one with a wider 'proper' fitting bearing.
You have one tensioner arm, and two idler rollers. Both idler rollers are the same width, BUT one of them only had a small width bearing in for some reason, i dont know why but it does, so RCMS just mod' it by fitting one with the wider bearing in it.
So all in all, not cheap, but for longevity and peace of MY mind, i had it all done. I still have the car now and dont look like getting rid, so well worth the money imho.
This is on a MY03 WRX.

if it were me i would change the lot for piece of mind £300 plus labour is a lot cheaper than having a rebuild should a roller decide to break up and jump the belt

There's also slowboy racing in brands hatch (the village).