Returning to work

Hi.
I have returned to work this week after being on Income Support for a few years.
I am a single parent of 3, so have had an interview at the job centre who said they would contact tax credits etc.

Anyway, they didn't so I have rung them myself today.

They asked for my income.
This is where I need help.
I am working full time for 10 weeks training, then I will drop down to part time.
So what do I tell tax credits- full or part time?

Also I wont get any wages until the end of May as we are paid a month in arrears. This is gonna be hard, has anyone got any advice?