I'll have a go at answering all the questions in one go..
CS Nuts - You have no excuse, get it done! You been before? If not, what are you doing man!
smr - You only need GA for Spa as 90% of the track is just grass banking. You cannot get to the areas between the final corner and the start of Eau Rouge without a grandstand ticket, but everywhere else is open. Decent views of Eau Rouge are possible, but difficult with GA. The roads around the track are indeed great fun. Its also only about 70 miles from the Nurburgring. Went a few years back and watched a camo'ed up Panamera testing, and a Ranger Rover sport where you couldn't hear the engine over the tyre squeel! Camping at the track is not recomended unless you are a fan of Finish Thrash Metal till 6am... I'm doing Camping F1 this year, which is a managed (they put up the tent for you!) site a few miles from the track so should be good. I have also stayed in the Formule1 hotel (basically a cheap Travelodge type place) in Leige, which is only about a 30 minute drive away.
Taken - GA tickets for the weekend will cost around £150. Then we are taking the Channel Tunnel at £120, although we could have got a Ferry for well under £100. Its about 400 miles from Calais to Spa so there is the fuel cost for that. Camping F1 is costing us £520 for 4 people for 4 nights in 2 tents. Camping at the track is cheaper, but I wouldn't recomend it, and the Formule1 place was about £30 a night. Its not cheap, but for the group of 4 of us going, including tickets, its been about £400 each to book, then we will just add fuel and food costs.