There will be a quarry somewhere near you, give them a call and they will deliver a 20ton load of material (part loads will end up costing more per ton and you will find 20 tons isn't actually that much!
The guy in the quarry should advise you on what is best (folk in the quarries near me are very helpful). Road planings are brilliant but like hens teeth. Type 1 is the standard material for roads, 50mm crusher run might be slightly cheaper (but don't get ungraded crusher run as it will have bigger rocks in it).
Don't know where you find someone to do it for you but ask about, there are a few farmers sons in my area that do that kind of thing.
If you are feeling strong, as it is only 1/4 mile you could fill the holes with a shovel and wheelbarrow but you will probably get fed up pretty quickly.
I would get a digger from the local plant hire place, £65 for a day (plus delivery) and borrow a tipping trailer from someone.