I picked up a cox's orange and a green delicious I think it was from Instore newbury a week or so ago, I put them in the garden near the hedge and now they have all but died, they got watered when planted and manured, now, I am just angry I killed my trees....
The current thinking is that fertiliser is extremely counter-productive when planting a bare-rooted tree...(and not great when you are planting a containerised one either) - at best you are encouraging the roots to stay at home by feeding them locally when you really want them foraging far and wide...
At worst too much fertiliser can burn roots especially the young growing ones - the fertiliser stops the roots getting water from the soil by setting up concentrated solutions in opposition to the osmosis you want.
The best thing to do is work and improve the soil as friable as possible so it snuggles around the roots, (but don't leave it too fine or it can waterlog), water well, and then put a metre square of black plastic around the base of the tree to stop the water evaporating. You can then water around this because trees expect to find 90% of their water at or around the drip line anyway.
If the land is badly drained (or for exotics like olives and guavas etc.) it's a very good idea to mound the soil for extra drainage but still put the plastic over the mound so you get the best of both worlds.
It works really well - I've never tried the un-recommended method but it sounds like you have!
Your problem is actually an opportunity - no gardening expert will ever recommend Cox (it suffers from disease problems unless sprayed within an inch of its life) and nobody with a sense of taste would ever recommend any of the (so called) "delicious" tribe.
Cheap apple trees are a waste of money if you aren't certain they will give you the result you need.
The maintenance costs (mostly time & effort) will make up 99% of the cost of the tree.
Owners of Siamese cats will tell you the price of the kitten is irrelevant when the mangiest moggy will eat several thousand quid's worth of cat food.
Get yourself an Ashmeads Kernel (RHS award of garden merit) or Claygate Pearmain instead of a Cox, and almost anything instead of a "delicious". I'd recommend Sturmer Pippin as an improved Granny Smith.
You need to choose apples like these that flower together or in adjacent groups (there's always an overlap) for pollination,
(
www.gardenaction.co.uk/fruit_veg_diary/fruit_veg_mini_project_september_2b2_apple.asp)
but you could go for any other of the apples given first-hand recommendations in the recent threads.
Or go to an 'apple day' in October when you can try before you buy...
Cheers.