Depend what I’m doin but local hardware to me stock pallet boards which are a great cheap way .
But if you want the fancier stuff like hardwoods or tongue and groove check with a local chippy they usually know the best places
Recycled Plastic Wood - Synthetic Wood - T&G - (W)100 x (D)18mm £13.95 inc. VAT
Made from recycled crushed CD cases, these tongue and groove boards will never rot, warp, splinter or crack, and are also UV protected so will never fade. A far more cost effective material compared to wood that comes in various colours and is environmentally sound.
Description
Ideal for Gates and Gate inserts. Synthetic Wood Tongue and Groove 100 x 18mm are guaranteed to last longer than any wood product on the market. Made from Recycled Crushed CD cases their benefits include:
Maintenance free - will not rot, warp, or crack
Impervious to water and frost proof
Have a much lower life costs in comparison to wood
Looks like wood, but behaves like plastic. Save yourself time and money by using Tongue and Groove Synthetic Wood.