Getting a lorry onto Midsummer Common is an arcane and exotic process, which changes every year at the inscrutable will of Cambridge Council.
I'd like to recommend D K Till, our local coal merchant, who has managed this feat three times in order to deliver 15 bags / £150 worth of coal directly to the roof of my narrowboat. He even lifts it up there, which considering I once put my back out throwing 25kg coal bags around is a very fine thing for him to do.
They're a very friendly family firm, father and son-in-law. All their smokeless coal is £10/25kg bag and they sell Taybrite and Supertherm, the most popular brands for boat stoves, as well as several other brands. It's hard work to get it any cheaper than that round here. Their coal is fine quality and comes in their own heavy waterproof bags.
I'm told, although I have not yet experienced this for myself, that they also sell wood, kindling, and gas bottles.
They have no web presence, so I thought I'd try to give them one with this post. Their phone number is 01223 232947 and I recommend them without reservation.