The worst ones are the small bolts that go through the rear bush console and screw into aluminium of the subframe bracket It seems to be a lottery if your bolts will snap or just come out - there is a galvanic reaction between the zinc galvanising and the aluminium.
In the picture below the troublesome bolts are not shown, but are located in top corners:
The other bolts should be OK - the larger M14's go into steel chassis. The smaller M10/M8 go into steel bracket -ARB & steering rack, you should be able to get penetrating fluid in from the top
On ebay: Subframe brackets are £15 to £20 a side and appear to be the same across all Mk5's & Febi do kits of rear console bolts for £6 a side.
If its the Nearside you are working on and its a DSG, you need to install the control arm into the subframe bracket before installation - box is too close, you cant get a bolt in...dont ask how I know and you will need a crows foot to torque it properly