I think that BK is from Norway, but you may want to search out his posts to check - he's the guy who's A2 has everything! There are some A2's around - the main difference is you'll see more Volvo's, Merc's and American cars than the UK. Strangly my Punto felt unique - I hardly saw any others, in fact I saw more A2's than Fiat's!
Although I don't have an A2 myself, I did last year spend more time in Norway than in the UK, including 6 months with my UK car in Oslo. I expect to by flying out for a long weekend in May to Oslo and possibly hiring a car for a few days. Last year I sailed Netcastle - Kristiansand which was a reasonable crossing in itself. I hadn't driven abroad before and found it easier than I had anticipated. Apart from major roads it's mainly single lanes, although they're building more. Compared to the UK there's lots of tunnels and they have many bends and elevations - great fun! If you get to Drammen (west of Oslo, second city), find your way to the hill on the east (spiraltoppen), make sure you go up - the road is inside the mountain and is a sprial - cost is about 10 NOK's, and well worth it. Up the top is a recreational area for walking, picnics and so on. There's more people who use the M25 each day than Norwegians, so as you could expect, even rush hour in Oslo isn't terrible traffic. I used to like parking my car at the Airport as I only ever saw 1 other non Norwegian car (Swedish) in doing so - the assistants still spoke Norwegian after seeing my RHD UK car. Most Norwegeians speak great English, so you wont have many language problems.
By law you need to have dipped beams on at all times, and spare bulbs and a warning triangle. Of course deam deflectors are a good idea, although it wont make so much difference if you're only there a week or two in the summer as there's lots of daylight! In Oslo over the summer I saw a few UK cars, but lot's of German, Swedish and Finnish. There were even some Italians and Spanish visiting by motorhome! it's definatly an unspoiled, beautiful, friendly place to visit. As you probably know it's expensive for some things (food), but at least fuel is around the same price as the UK (diesel being cheaper than petrol).
I have a couple of maps (Norway whole and Oslo specific), that are available in most petrol stations, but you're welcome to borrow them if you want (I think they cost about £15 a piece). There are toll's to pay going around the country and into Oslo, but nothing like the £5 a day of London. 15-20 NOK is usual, and it's often to recoup the cost of building a road or tunnel. Credit cards are accepted almost everywhere (I now find it annoying that UK fast food restaurants don't take them!), including taxi's.
Feel free to ask anything else, I guess having lived there as a foreigner I can see the differences betetr than a local, but don't know enough of the country to give a fantastic route for sightseeing.