"You can do Donington without a bus if you go on the Saturday, if you don't mind about a 2 mile walk. Just get the train to Derby, get the bus to the bus station (about 20p) and then get the 68 bus to Melbourne. If on a bike, and coming from the East/West/London St Pancras, go to Derby and follow the signs for Allenton, Chellaston and then Melbourne, from whence take the Castle Donington road for the last couple of miles to the circuit (not too pleasant on foot but I do it quite regularly). This bit is short but hilly. Alternately, especially if coming from the North/South try to get a convenient train to Willington (the long distance ones don't stop there so change at Birmingham New St, Burton on Trent or Derby) from whence you can ride along the old A50 past Willington Power Station (or what's left of it), through Barrow-on-Trent to Swarkestone, at which point the road ends and you turn right and join the other route over Swarkestone Bridge to Stanton by Bridge and on to Melbourne.
Both routes are similar in distance, depends how the trains fall which to pick. If you can go to Willington without much delay to your journey, I suggest you do that.
Melbourne has lots of pubs, a Spar shop, motorsports garage, bakery and all sorts so get your nosh here.
At the circuit, sneak in behind a lorry as he stops at the main paddock gate and then turn left into the camping area (if full, go back out and ride down to the museum round the back of Starkey's straight where there is almost infinite space). As you're not actually camped inside the circuit walls you can come and go as you please and I advise you to go to Melbourne of an evening."
"Get the train to Long Eaton. This station seems to be at a junction of lines, so you can get there from several places, the easiest is Derby. If you're on an Intercity, make sure you put your bike in the right guards van because it's only a short platform. On one side of the lines is a car park. If you're on this side, go under the railway, and follow that road, follow signs for Castle Donington, or the M1. You have to cycle under the M1, about 6 miles to Donington. I've only done this once (April '99), and it took 40 mins there, 20 mins back, because the wind was strong."