When I did my rear shocks I used a combination of penetrating fluid and a 1200degree C blow torch, this was successful but did result in setting the suspension alight a few times. (Many many times) now I have air impact driver I wonder how I've lived without for so long makes light work of so many things without the same risks of shearing seized bolts, you can also buy a fairly decent electric version for about £45 if you don't have a compressor