Forget the sheds, use the local builders merchant, generaly cheaper and delivery is better.
Agreed, ignore at your peril

You go into the store, pay and they order the stuff for you. It then gets picked at the suppliers, usually in cubic yard bags. These are then palletised and sent out on the cheapest pallet service available. A week later, once you've forgotten about it, a 30ft truck will appear in your road with a pump truck and a taillift. If you're really lucky and the run to your drive is smooth and basically level, then your delivery will be put in front of your garage door. Any kerbs, gravel or block paving and you'll be spending two days with a spade and a wheel barrow shifting it from the road side. Same applies to internet orders, even direct from suppliers, and especially if delivery is free or cheap
Always buy bulk material from builders merchants. If you clear the ground before you order it, the local builders merchant will drop the bags over the wall with a HIAB, no fuss, no drama.
B&Q etc are great for late weekend 'Oh bugger I forgot to get...,' moments or little projects, but they are quite disconnected from a delivery perspective...