At the moment i only use my local shop Marks Water Garden in Teddington,the only thing i buy is live food and RO water.
With the heat weve been having its not really fair to judge them for the tanks been too warm,they do have 4 huge fans which circulate cold air around the shop but when its in the region of the low 30s outside there not really much anyone can do.
But i have to agree £4 for a few meters of tubing does sound a little steep,are you sure he gave you the right price?