When I had my chain/tensioner done I sourced Genuine parts myself @ £200 (would likely be more now). Then garage then charged 5ish hours labour, so depending on labour rate/genuine parts, £600 sounds about right. Id personally be reluctant to go with anything other than genuine parts for this job (then again I like to use genuine parts everywhere).
Also, there is an additional component in the chain/tensioner area - the cam adjuster. This part alone is circa £300. I didn't have mine replaced, as many others haven't. But if something goes wrong with the job or if this part is deemed to be damaged, it could be an additional expense.
Parts required (the site I used to use to source parts from Germany direct no longer exists so equivalent prices at TPS may be a bit more):
06D109229B
CHAIN £79.50GBP
06F109217A
CHAIN TENSIONER £82.98GBP
06F103483D
VALVE COVER GASKET £12.98GBP
06D109281D
SCREW £1.67GBP
06D103121B
GASKET £4.54GBP
N10196303
BOLT £0.37GBP 3
N10124308
BOLT £0.26GBP 7
N90739901
CLIP £0.75GBP 2