Just pressure washed the decking for the first time this year, and boy
did it need it! Now back to looking "new" again, and I hear that
decking oil is the way to go for a bit of protection. I don't want to
affect the colour of the wood if possible (it is the usual pressure
treated / tanalised ridged decking). Are there any recommendations on
the choice of decking oil?

Screwfix do a cleaner and oil combination pack from Ronseal, which
appears to be "natural" colour.

THey also do Cuprinol's "natural pine".

Does anyone have any experience with either? Before I go ahead, what
should I expect to happen to the surface of the wood when it is
applied? Will it have a sheen?

Thanks!

Matt