I have found this thread but it seems to be outdated
According to http://driveeuropenews.com/2015/01/21/sweden-21/
The final UK-Scandinavia ferry service, operated by DFDS between Harwich and Esbjerg, Denmark, was withdrawn last September
the start of services – likely between Newcastle, Bergen and Stavanger – the following March
So 2016 March might just see the resumption of ferry service although from Newcastle not Aberdeen.
However http://britishscandinavian.com/ still have nothing firm.
There isn't a ferry per se, but plenty of cruise ships sail from London Tilbury and Southampton to the Norwegian fjords. Some cruises allow you to only book a part of the journey, so you could use the cruise boat as a fancy ferry. Cruise prices start at around 100 EUR/day and it takes about 36 hours to reach the fjords, so in theory you should be able to pay as little as 200 EUR to get to your destination. Here's a link to one of the companies organizing such cruises.
As a bonus you get to spend your journey in a comfortable boat with plenty amenities.
There is a commercial ferry service on DFDS between Brevik and Immingham, but they are unable to take private passengers. I suppose you could hire a van and claim you were on a business trip, but the cost £745 pounds is about the same as you would pay for a cruise like JonathanReez suggests.