Hello,
I can perhaps begin with the vegetarian food, as a vegetarian. In Oslo it doesn't usually cause any problems. Most restaurants will have at least one thing to eat. It won't always be very exciting though. Some restaurants are quite good with vegetarian food, you just have to seek them out. If you leave Oslo, being a vegetarian can become a major problem. That goes for most of Scandinavia from what I have seen. Most Norwegians think it's extremely weird not to eat meat, and don't consider something food unless it has meat in it. Attitudes are changing though, particularly because of the increasing number of immigrants. The quality and variety of food in the supermarket is also improving, although the government does regulate the food supply, which leads to very high prices and occasional shortages of certain things. You can buy some meat substitutes in many shops, such as Quorn and the Swedish versions of that. I have even managed to find one shop in Oslo selling vegetarian bacon. Although it is expensive. In some ways being a vegetarian is good, since the price of meat here is extremely high due to government controls.
Many immigrants I know struggle with the social side of things. Many Norwegians have their group of friends and are not that interested in making new ones. This is particularly true in small towns. In Oslo I don't think it's quite so bad. Norwegian culture seems to think that talking to strangers is an awful thing. So getting talking to someone, and then getting past that initial stage can be very difficult. In my experience, Norwegians do not make friends with their work colleagues in the way that happens in many other countries. They are of course nice to the people they work with, but don't expect to be going down the pub on a Friday after work. This seems to be extremely rare. In fact, it is more common to visit your friends' houses rather than go out, which again can make it hard to meet people. There are of course a lot of foreigners in Oslo though, so that will give you a chance to meet people. Norwegians are also very nice people when you get to know them. You shouldn't mistake their reluctance to talk to people for coldness of unfriendliness.
As for cultural differences, I think coming from the UK is an advantage. People in Norway are familiar with the UK and generally very positive towards it. Many also enjoy the chance to speak to a native English speaker in order to practise their English. This can work to your advantage and can give you a chance to get to know people. I think sometimes Norwegians will make exceptions to their regular social rules when it comes to Brits. I have made some Norwegian friends this way. Another difference a lot of people notice is that the Norwegians may appear rude. In fact, it's just a different sort of politeness. Because Norway has been a rural country until recently (and still is to some extent) people have not developed all of the social norms associated with an urban society. They will generally try not to disturb other people, which can sometimes translate into them ignoring other people. To Brits and many others, this can come across as extremely rude. You get used to it though, more or less. As a culture they are very keen on concepts like fairness, equality and democracy, although sometimes the definition of these concepts are rather fuzzy. It seems to work to create a nice environment to live in though. I think it also works in foreigner's favour.
The cost of living is shockingly high when you first arrive. After a while you get over the shock. So long as you have a decent salary, it's not a problem. There are some things which are disproportionately expensive here, which you might have to do without. For example, owning a car is incredibly expensive. Housing is also expensive at the moment, but I think we are on the verge of a housing market crash. Prices are insanely high, and have been financed by a book in consumer debt (sound familiar?).
If you have any specific questions, just let us know.
David