You can contact his solicitor but first you need to tell your solicitor that you're doing so, and ask her to write to his solicitor tosay that it's ok for them to contact you direct.
I occasionally get mail from the opposing partner when they have a solicitor on record as acting for them and am obliged by the rules to tell his solicitor and copy them in on the correspondence. You can avoid incurring these extra costs by doing what I suggest above.
Is your solicitor advising that a sale of the fmh is in your best interests? It may be better to get your ex to buy you out, if he can afford to do so. Remember that you may be entitled to more than half of the equity if you have the kids living with you and if you earn less than him.
When you do contact the solicitor for your ex, make sure your letter is headed "without prejudice" so you're not binding yourself to anything. Ask your own solicitor to give you a guideline of what you should be asking for (eg, 70% of equity, plus nominal spousal maintenance, child maintenance, pension sharing order) and put that forward in your without prejudice offer.
Say that unless they respond positively within 21 days you'll issue proceedings for ancillary relief (for the court to decide).
If you hear nothing in those 21 days, file Form A at court with the issue fee of £240. The court will then impose a timetable for things to happen, in particular for you both to file Forms E, statement of issues, chronologies etc. It will then hold a brief informal hearing and in many cases the case can be settled at that point, but if not, at the next stage.
As an alternative to going it alone, you could get your solicitor to ask if your husband will give you an interim lump sum of £10k or so to pay your costs. That lump sum will then be deducted at the end of the day from whatever your final settlement is.