I've done Barcelona, Valencia, Brno and of course Silverstone but only 1 of which I travelled on the bike (Brno).
Barcelona was a group of 5 of us and we went in my van with all the camping gear - our first 'abroad' gp. The adventure was in the driving - all that way down through france and of course back again. I almost killed us coming back having driven for 22 hours straight I had a bit of a snooze at 80mph on the M1 .. luckily I'm a light sleeper! Suffice to say i got my head down at the next services.
We camped at the track at the official camping ground just across the road from the circuit but were just not expecting the levels of dick-headed-ry from our fellow campers. Next time, if we camp there again, we'll have a bit more of an open mind and I'll add some time before and after to prepare and recover. Showers and toilets are *disgusting* though - the toilets at the circuit are actually better, so caravan, campervan would be wise here - or hotel/BnB near Montmelo. Cant really comment on the roads - we only hit the highways and the occasional dirt-track road when lost and we used the motoroways all the way through france except when the sat-nav diverted us due the monster floods that france had at the time. The diversions were very pretty though. Event wise, pretty good - the Monster village here was (so far) the best one I've been to. We viewed from turn 7 on the grass banking, which wasnt the best vantage point, next time I think i'll find somewhere a bit further around.
Valencia was done in the car, using the 24 hour ferry from Portsmouth to Bilbao and was one of the most enjoyable gp's I've been to because I dumped the car when I got there and used public transport to get into the city and out to the track. We had a couple of days either side of the event for some sightseeing which made a big difference. We stopped near the beach in an airBnB flat so none of that noise rumpus from the scallywags at the campsite for us here, and valencia is a very pretty city.
We did venture out on our last day to visit some potential properties but we were taxi'd around by the estate agents who had excellent local knowledge. Most of our pretty sights were from tiny back roads but there were plenty of them, some with incredible views over the nature reserve (or green-belt equiv). The event here was ok - not as full entertainment wise as Barcelona and def not as interesting as Silverstone but as it was the last race of the season, it was *rammed* with plenty going off at the vendor stands. We did manage to get some paddock passes due to the offspring and missus being in the DK52 fan club which made the event a bit special for us. Viewing at this circuit is brill - take some binoculars and you'll be able to see most of the track.
Brno was a long slog on the bikes. We had zero spare time due to my nephew having to be back at work so it was 99% motorways there and back - long and painful (aches) but certainly an adventure. Czech is very friendly and Brno is quite cheap to eat/drink in. We didnt encounter any tolls on our journey either - didnt require a motorway pass as we were on bikes and with the exception of the Czech motorway condition, had a real good experience. The 1% where we were sat-nav'd off the main routes were spectacular - just wish we'd have had time to get off the bikes more and take some pics of things other than petrol stations. Viewing wise, the track is pretty good - lots of high vantage points. Food at the track was cheap too - or should I say, 'reasonable'. Certainly not worth taking your own food unless you hate queuing. This is a big track to walk around. Dont listen to the young tools they employ at the security check points for directions - ended up walking for ~4 extra miles to get to our free shuttle bus back into Brno city 'cos they'd sent me to the normal public bus stop on the main road..argh.. not fun after a day of walking around the track, think I hit about 13 miles on the iphone health tracker thing that day.
I've just booked accommodation for Mugello next year and the missus has booked her flight - I'm on the bike on my own, so will make sure I get time to enjoy the journey properly rather than just head down tarmac beating. I'm still considering options for EuroGP 2 - prefer the warmer places, so perhaps I might do Brno again and avoid the motorways this time. Ever had that feeling that you'd missed some spectacular roads and scenery by a few yards? That itch needs scratching.
