Help! Advice needed... almost sold house but buyers keep asking for more info

[Jaxxmac]

Hey! Can anyone help? We have sold our house with leasehold garage but just as we are about to complete we've got a snag!!! Our garage is under a coach house. The CH owner had the wrong insurance and this prevented the sale. They have begrudgingly and slowly resolved this and we have provided an estimated cost per month of our contribution to this insurance to our buyers along with proof of insurance and policy no. They have refused to complete until we provide them with the policy, CH owner won't provide it until they sign the lease and we are going no where fast. Solicitor said this was all that was needed but the buyer is adamant they have to have this insured to get their mortgage. Can anyone shed some light? Hubby is ready to kick whole process into touch, home atmosphere is not good right now... argh!