How comprehensive does this set need to be? Dinner sets are very individual things - taste wise. Do you want a specific colour or design? Argos Ebay have this set: https://www.ebay.co.uk/itm/Argos-Home-18-Piece-Ceramic-Microwave-Dishwasher-Safe-Dinner-Set/362693836644?hash=item54723cbf64:g:QFoAAOSw6rFejXLb 18pc - £15.00 C&C. Just plain white. Perhaps see if available near you? Also, Ebay: https://www.ebay.co.uk/itm/Arcopal-Zelie-Dinner-Set-White-18-Piece-renowned-for-its-durability/124266912170?epid=2005678190&hash=item1ceee299aa:g:EAEAAOSw7z9fFXfR £21.97 delivered. Again, plain white. Plenty of others on Ebay too. Nice ones with patterns but a little bit more money. Hope you can find something suitable. Regards, Phsy.
Ikea have some 18 piece sets https://www.ikea.com/gb/en/cat/dinnerware-18860/ I got mine from Sainsbury’s, I got 2 sets for 4 so I had enough for six people and spares in case of breakages. Asda have some nice sets too.