Theexwife
I would speak to him first about parting, the more amicable it is the quicker the separation can happen and the cheaper the solicitor would be.
As above. There is a website for a firm of solicitors "Amicable.io" - I won't do the link as there may be cookies on it - that has some interesting information (not suggesting this firm, just the information on their website) - the more amicable the decision the less costs for solicitors - hours spent in checking pensions, bank statements etc.
We had a fairly good mediator suggested by my solicitor who was - my opinion - unbiased and worked hard to give a good overview / representation of our finances, earnings, pensions, etc. Now-ex had moved out 8 years earlier (chasing after a younger woman who was horrified and disappeared quickly). Was a nightmare as right at the beginning of Covid, getting information out of Pension companies was delayed, which now-ex got exasperated about (it was his pension information we were waiting on!!) and now-ex insisted on proceeding without that information and the mediator firmly told him that wasn't going to happen .. Ditto his vehicles, she told him it was unreasonable to own 4 motorbikes and a car and not include these as assets (her saying to him "you only have one bottom" was joyous) - I know he'd have battered me down on both points above if it were just left to us, or hundreds in back-and-forth with solicitors. I pointed out he lived with his girlfriend of 3 years - he denied this (despite Google maps showing his car outside her house) and the mediator took him at his word in that he'd need necessary funds to buy a new home for himself (three years on, still lives with his girlfriend). As it was, for a fairly straightforward sale of house / split of funds my now-ex showed himself to be a vile obnoxious odious man and I look back on that time as the reason why I never want another man in my life ....
Frank conversation first, then look at mediation with a solicitor to guide you if necessary is the "cheapest" way. Good luck.