Insulation not needed!!!!! What part of Yorkshire is a tropical micro climate
Heavy mass is best sound insulation, so insulate first, then 12mm ply lining, then MLV (Mass Laden Vinyl) then further ply lining, 18mm best. If you stagger the frame uprights by an 10mm and secure outside to each upright on outermost side, and the inner lining to every other upright on the inside, this reduces sound transmission from inner surface to outer surface.
Don't bother with the acoustic foams for sound proofing, it doesn’t sound proof anything, but it will deaden acoustic echo inside the work space, great if you plan on recording in the shed, ie youtube videos, but useless to prevent sound getting out.
Also you need to seal around doors and any gaps to prevent sound egress. But you also need air flow to prevent condensation forming. Unless you plan on having a dehumidifier, that you can drain directly outside, without compromising soundproofing or sound transmission.
As you can see from above, good sound insulation is both time consuming and expensive.
Best of luck in balancing the cost, time, effort soundproofing needs.