“But we’re agreed on the divorce and the financial arrangements so we don’t need separate solicitors”.

Yes, you do.  If you are getting divorced there is an intrinsic conflict of interest and you each need to take advice separately.  Sometimes what seems the obvious thing to do, for example sell the house and divide the proceeds equally, is a fantastic deal for one spouse and a disastrous deal for the other.  Always take advice – your own advice from your own solicitor.

Consider the following analogy:

If I sell you my car for a price which we agree at once without any negotiation, there is still an intrinsic conflict of interest: your interest is to pay as little as possible for my car and mine is to get as much as I can for it.  The intrinsic conflict of interest hasn’t gone away just because we don’t haggle over the price – and of course the agreed price could still be too high or too low to be a fair price.