[speedtail001]

What kind of parts are you looking for? Do you think a WIR would work out?

drivetrain, casette, rear deraiuller, front fork. Theyre all about over 300£ ish. ( proper mtb stuff  ) whats a good weight for wir?

There's no specific weight for a WIR, but the two items you're going to buy must match as close as possible an exact weight.
Also, picking an item from the same kind of item you want to SE improves your chances of succeeding.

by two items what do you mean?