I have a number of unused telescopic underfloor vent sleeves & compatible "air-bricks" - see the Screwfix listings for more info - https://www.screwfix.com/p/telescopic-underfloor-vent-black-220mm-x-215mm/1... & https://www.screwfix.com/p/air-brick-terracotta-76mm-x-229mm/13873
Can deliver in Craven Arms, Ludlow & Bucknell areas by arrangement