Am looking for some advice on the advantages/disadvantages of types of
decking.

Am planning a patio and path scheme for the garden.

Have priced up at the local Timber yard and have estimated materials,
including joist and fixings at:-

approx. £300 Redwood Reversible (38mm x 125) and £500 (28 x 145).

Could someone kindly advise me on the pros and cons of Redwood v Hardwood
and the thickness.

Not a good idea in a cool damp climate like the West coast of the UK.
Decking works fine in places like Southern California but readily gets
slippery if the climate is damp.