freelancing for games company

just wondered if you had any idea whether its best to go freelance (ie set up a company with me as the sole trader) when working for a games company, or as full time employee but on a short term contract.

If the former is better, should I ask for a lot more since they won't have to pay company tax or buy software or equipment for me

I have been offered a 6 month contract and TBH I don't think the money is so hot, only 2,000 more P.A. than my last job.
I was told by my agent that I should ask for a minimum of 200 pounds a day, but in my experience working for games companies, they never offered even close to that unless you were very senior - art director or similar.

Another worry is the nature of the work. I don't think it will benefit my career long term, its basically optimizing pre existing assets, which is pretty much donkey work.
I hate to turn it down, but I fear that because I am new to freelancing I am going to get stung due to my lack of negotiating experience and knowledge of how stuff works.
They also want to me fly up to their offices every 4 weeks and work in house for a week , which kind of defeats the object for me as working from home was an attractive option for me.
I am sure a week could easily turn in to two weeks if there were any tech problems to resolve.
BTW I am not new to games art, been working as a senior artist for a while, but am new to freelancing.