>First question I have is regarding the type of apple juice you all use. Here in the UK, the majority of apple juice sold in supermarkets & shops is made from concentrate, then rediluted to the same strength. Some places also sell 'not from concentrate' apple juice, but this is much dearer. Would diluted concentrate be ok?
It will be alright, but is not ideal. With Cider it is all about the base product. There is really not much to mask anything off that you can get from some products. It's a start though, and I am sure will yield something great, perhaps not ideal though.
>From later this year I'm hoping to get free apples from a friend who has a small orchard area, so really I want to get it right with cartoned juice first so I'm ready to crush & press my own.
Try to find a small press, locally. Pressing on your own is a lot of work, especially if you don't have good equipment.
>I'm also considering adding fruit (cherry or stawberry) to one of the demijohns. Could I try using tinned black cherries or similar, as long as there are no preservatives etc present (just cherries, sugar & water)?
Yes, that is a very good way to proceed.
>Plans are to brew it in my spare room, which usually has the curtains closed and stays between 18-22deg C (65-71 deg F for you yanks

)
That will work fine
>Any other advice? Plan is to brew it then transfer into bottles with some extra sugar to store. Not too worried about carbonation, a little would be nice but still is always good.
You don't really need the extra sugar to store it. I personally like my Cider highly carbonated (for now anyway).
>Can't wait now: had a pint or two of H. Weston's Old Rosie at the weekend and fell in love (if it doesn't mean anything, google it: some tasty stuff!).
Keep in mind, they are using Cider apples. Blending Bittersharps and Bittersweets, etc, to get the profile they want. Not trying to discourage you, but if you want to aim for that it will be a bit of a challenge. (I personally have plans on adding some Bittersweets to my Orchard next season).
>Hardest bit will be waiting for it to be ready before I get my hands on it!
It does take quite some time, but is well worth it. Keep us posted, and if you have any questions everyone here is more than glad to help!
Welcome to the forums!