So late, I hope not too late, at least for next season. I used another few bags last week and it really is amazing...!

08000 430124

or anytime:

07990 970461

You can tell him you were recommended by the Old Marston and Upper Wolvercote Alloments!

Any luck on finding that number?

The best locally available horse manure (rotted, bagged, screened) is called Wilgrow (willgrow?) and I will post the number for them as soon as I've gone back to my allotment where the card with his details is! Google searching so far provides little... perhaps this really is a business still working on pre-email footings! The stuff arrives in a very smart pickup truck and is delivered by a very smart man and costs about £6/bag (sort of compost bag sized).
Otherwise, there are other people who will deliver more for less, but this is a) not bagged and b) probably not screened. Expect to pay about £40 for 6cubic yard trailer loads.