I concur that manure in bags if at all possible is the way to go. I have dug about 3 cubic meters each of the last 2 years, limited mainly by my time and it was a bit of an obstical course. climb gate in to friends barn and shovel in to feed sacks, lift over gate and in to back of car with the help of friendly cows (I was using old feed sacks and they clearly recognised them. Drive half a mile to alloments load in to barrow then tip on to allotment where needed. I try to do 2 trips per week over 2 to 3 months. It has produced some excelent crops this year an made a noticable differenct to both the soil life and water retention in my light sandy loam so well worth the effort and a lot cheeper than gym membership 
