Hi Ian.
Get your self an Aviation spanner and grind the end down, it is 24mm for the tensioner pulley, to change the large belt and 22mm to change the small belt
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Link to Aviation ring spanner
https://www.ebay.co.uk/itm/Flat-Avia...AAAOSwuGxZlWpj
You could even purchase a set of Aviation ring spanners they are very useful indeed
https://www.ebay.co.uk/itm/BERGEN-7p....c100005.m1851