Wilkos do a knock off type Lego called blox that is compatible with Lego, I haven't used before but I got 2 of these for my boys for only £5 each- they look fab! Apparently they sold out really quickly last year, the very kind shop person went out back to get them for me as they weren't even out yet.
https://www.wilko.com/construction/wilko-blox-advent-calendar/invt/0417599
(They also have some lovely pumpkin candle holders!!)
https://www.wilko.com/construction/wilko-blox-advent-calendar/invt/0417599
(They also have some lovely pumpkin candle holders!!)