Yep, the same company also does self levelling plaster! What do you mean by ' self leveling'? Ah, do you mean levelling clips and wedges?
Tbh, I've only just started using them myself and bought some off eBay. You must still ensure that tiles are set correctly, they won't compensate for for shoddy work.
Is this what you are looking for??? https://www.screwfix.com/p/vitrex-lash-tile-levelling-system-trade-pack/8419f Alternatively there are these - https://www.tiletown.co.uk/en/genesis-tile-spacers
I use Suretile spacers, available in various sizes & reusable,available in packs & tubs. https://www.ebay.co.uk/itm/Suretile...538572?hash=item233d31f14c:g:y8sAAOSwwpdW8VuX https://www.manomano.co.uk/tile-spa...um-heavy-duty-tile-spacers-2mm-or-4mm-1737806