Re: I'm going to go out on a limb...
I'm not UK based so no IR35, but we do have mutuality of obligation built into the contract. Reason being that I'm currently performing a critical function and am in theory not easily replaced (although I suspect I'm easier to replace than they think, they're just lazy), so they wanted a 3 month notice period.
Also no timesheets. It's a fixed-term employment contract with a defined end date. I'm not going to get into details as it could make me identifiable, but where I currently live the law allows for up to 3 fixed-term employment contracts before the company either has to offer you fulltime employment or not employ you for a calendar year.
The concept of risking being told 'we have no work for you' and shown the door is alien to me. I'm sure it happens, but it's not a contractual basis I or my employer would be happy with. I presume it works both ways, in that you can also walk away with same-day notice?
Biting the hand that feeds IT
