It was fantastic, so much so we're looking to go at the end of May and August too!
A lap was about 23euros, I only did 3 or so to keep the costs down. Even with 3 I need new pads and the tyres are worn
My last lap of the trip got me under the 10minutes mark which I was happy with.
The journey there wasn't too bad, we landed at Dunkirk at 8am and got to the hotel (which was at the halfway entry point to the 'Ring) for about 2:30pm or so.
The journey back was a nightmare, traffic in Belgium made us miss our Ferry, but the Ferry people were understanding and booked us on the next crossing FOC
The trip used about 5 tanks of fuel in all, my LCR used just under 1/4 of a tank per lap! Thirsty bugger. with 2 tanks or so each way. My friend and I split the cost of fuel and laps which made the trip much more affordable.
I'd thoroughly recommend going, just don't try and be a hero on the track. There was enough of those closing the track 3 or 4 times a day!