The following is based on the fact that this is one of my practice areas:
A Nikah MAY be recognised in English law - it depends on many factors. OP needs to seek out a solicitor who specialises in this area (or at least has detailed experience of it) as they will need to go through everything that occurred, as the devil is in the detail. The OP MAY be legally married in English law - no one can tell as from my reading the OP hasn't given the detail required to make that determination.
The OP is entitled to her Mahr, if it wasn't already paid, so she should attend the meeting with the Imam to ensure that the Talaq meets the relevant requirements.
For the purpose of Sharia law, the OP is indeed married, and the Talaq is a divorce. Whether or not she is married under English law remains to be determined. If someone assesses all the facts and determines the Nikah is not a valid marriage in English law, then under English law she will be treated as a former cohabitee, with no financial settlement, no legal divorce, and entitled to claim child maintenance.
But if her Nikah is determined to be a valid marriage, then a formal English divorce will need to take place and a financial settlement can be applied for.
(I won't be answering specific questions, that would fall in the realms of giving legal advice and I don't do that for free - see a specialist solicitor.)