Remember that IR35 isn’t as simple as ‘I worked there six months and look at my contract’. It’s based on actual working practices. If you are working for an Umbrella, you don’t need to worry about IR35.
http://www.contractoruk.com/first_timers/
Sit down and do your sums. Day rates might look good, but all of the stuff that your company may have paid for or contributed to, are now for your expense. This includes the obvious stuff like pensions, medical schemes and holiday, but then there is certification, industry seminars you may attend, stuff like that. Build in a healthy amount of time on the bench into all your calcs.
To back up what allthepies says, do the research, and be honest with yourself, about how in demand your skillset is.
Remember it is running a business, and there is a certain amount of work that goes with that. Gone are the days of an amount of money appearing in your bank account at the same time every month. It can be frustrating at times.
After all that though, I’ve actually just gone the other way. I’ll be starting my first perm job next month after nearly a decade of contracting. The past 2-3 years have been a constant ‘one step forward, two steps back’ scenario, and I have had enough. Time for some consolidation, and then I can rethink it.