http://www.parkfarmhouse.co.uk/
is almost straight outside front entrance to DP but probably booked up that weekend
prob next closest –
http://www.beehivefarm-woodlandlakes.co.uk/
for a full list see here –
http://www.lovecamping.co.uk/campsites/east-midlands
DP is in Leicstershire but with a Derby postcode, so any in North Leics, S Derby or NW staffordshire will be within spitting distance
If you want halfway between Donington and peaks then there is a couple on that list around Belper / Crich way, just beware the A6 though Belper is closed at weekends at the mo
there is a decent half days riding to be had straight from Donington ,around Ticknall etc – check the STW route guide for 2 routes, they can easily be extended
Cannock is 40 mins away, peaks 75mins, sherwood pines 60mins, ambergate/north derby area etc also has good riding – just join together bridleways of the OS map and explore