First problem is the lack of access to the Adjustment nut, A Ratchet Spanner proved to be the solution.
Second problem (The reason for this post) was the Alternator Belt that I bought from Halfords,
Halfords specify the Part code HB763a this is actually the Air Conditioning Drive Belt.
The staff ever helpful said the specified belt was correct because the COMPUTER said so!
After the use of an Orange Cone and a few different belts I eventually found the Belt that fits.
So if you want a Alternator Drive Belt from Halfords Ignore their Application chart and get Part Code HB600a
Alastair