Hi July..
Your sentence "we have a conveyancer only who has been very " seemed unfinished..
I think if I were you I would say to the vendors, look, take as long as is necessary, but you will have to pay any additional costs we incur due to the late settlement, but we won't charge you penalties.
This is the nice alternative. It wasn't the vendor's fault that the house was damaged, and they seem to be attending to it's repair in a timely manner.
In my humble opinion, it shouldn't matter in a case like this whether you are dealing with a conveyancer or a solicitor. (The only time I feel that solicitors are a distinct advantage is where there are other than conveyancing issues involved, such as trust setups, or development plans...). The other thing to remember is that all conveyancers are 'Backed up' by a solicitor.
This means that if there is something your conveyancer doesn't know or isn't sure of, they can get solicitor advice.
That being said, if you really want to change, PM me and Iwill give you some numbers.
Talk to the conveyancer, and see what they say.
hope this helps
asy