Hi Lynn, and welcome to the forum.
I am with Accuma as well. I send them my payslip each month, and if I earn any overtime or receive a bonus I have to pay half into the IVA. This is one of the standard clauses in an IVA, and if you think about it, it's quite fair. By allowing us to keep 50%, the creditors hope that it will encourage us to do overtime.
If you are struggling with your payments, you really must contact Accuma ASAP. I have found them very approachable. It is better to talk to them now, rather than keep struggling.
Regarding the bankruptcy company - be very, very wary! I don't like the sound of them asking for £1500 up front. As far as I am aware it costs less than £400 to petition for bankruptcy yourself. To be honest, I wouldn't touch them with a barge pole. To me, anyone asking for a large sum from people who are already in debt are just taking advantage of our circumstances.
As I said, I would contact Accuma, explain everything and take it from there.
Good luck and keep posting to let us know how you are getting on.
Three down, fifty seven to go until freedom!