It appears that when I bought my car the previous owner may have removed an aftermarket stereo taking with it the booster which I guess is required with the shark fin aerial.  I am about to order tools to remove the stereo but was looking for confirmation of which booster to buy. On ebay the Autoleads PC5-52 and PC5-90 are both listed as compatible.

 

 

I'm pretty certain that the Autolead devices you are looking at do not boost the signal. They are a way of connecting your coax aerial cable to the car's 12V + supply. 12 volts is required to power the signal amplification circuit at the base of the aerial (assuming there is one). Many radios (and certainly the one origionaly fitted when your car was made) have an integral 12 volt supply for the aerial cable.

Try and find an expert to check this with. Cheers