fixed fee company

I have been in financial settlement negotiations with my ex-husband via my solicitor for a good 18 months, to the tune of £9k in fees (none for him, he is self representing), and was at the point of signing a deal last week.... when I came across a newly set up company who quote you a fixed fee for *all* of their work to get you to settlement and Decree Absolute - in double quick time, no more back and forth with endless letters, including if your case ends up in court. Their fixed fee is £8k plus VAT. They sound too good to be true! There's some small print that says there may be extra solicitor costs but that's not clear under what circumstances... eg if my ex contests their proposal, then what happens? They haven't been operating long, and don't appear to be registered with the FCA... They have today drafted and sent me a proposal which is an infinitely better deal than I was about to sign up to with my original solicitor. My ex-husband will be livid if I go through with this change of tack as he will be out of pocket to the tune of an additional £125k, plus child maintenance at £500pm for the next 10 years (which my current solicitor had said was not possible). They say the deal represents an exact 50:50 split of assets, however, (ours was a long marriage at 12 years) and that my original solicitor simply got it wrong / can't do maths / my ex was being shady with his versions of the asset schedule and hoodwinked her.
Has anybody else had experience of such companies, and am I right to see red flags in this?
Am at the point of jumping ship but don't want to throw good money after bad... !
TIA for any advice, A

what someone tells you you will get and what a court signs off are different things

2 solicitors nearly £200k apart on their views suggest more details may be required. What if you pay £8k and you end up with the same deal as you originally agreed?

Your best bet would be detailing the state of affairs and money at stake and people may have a better view though speaking to a third solicitor (or the helpline here) for an overview may also have some benefit before you sign up to any further costs

Thank you for your thoughts and advice, Rickoshea - I wasn't sure if it was appropriate to put that level of detail in public forum.
I agree with you that the deal doesn't necessarily happen just because they say it will.
Very unsettling that there can be such disparity in opinions from two professionals!
VMT's, A