what are my rights???

[flix]

I was supposed to return to work next month and requested to return 2 days a week. They refused and said 4 days only, after chilcare and travel costs I'd earn a pittance each week. So I had to refuse and thus resign. That was last week, today I found out that we are amalgamating with another office and we can get redundancy packages. I am soooo cranky as I could have gone back, worked for a month then recieved redundancy!!!! what can I do

Looks to me as though there could be more than one issue here, seeing that redundancy could have been an option.

Call ACAS - 08457 47 47 47 - Monday - Friday 08:00 - 18:00 They can give you general advice and have publications that may be handy.
ACAS Website

I'm about to go on maternity leave. Can I ask to return part-time?

If you can reasonably argue that they'd have known about the upcoming redundancies last week, and thus deliberately turned down your request in order to force you into leaving and thus saving themselves the redundancy payment, then you might have a case for constructive dismissal. Did you go through the formal request for flexible working procedure, or was it just a verbal request?