After another attempt to call my solictor yesterday, I tried again this morning, she again wasn't available, but the man who answered when I said she doesn't answer emails or return calls said he was her supervisor.
It turns out that even though I paid for searches 4 weeks ago, they've not been ordered as they don't request them until they get the contracts from the vendors solicitor. I had no idea on this.
When I called last Wednesday so understand progress, and again got someone else, that person told me they hadn't received the contracts, but she chased them that day and they were being sent that afternoon.
Apparently, the contract has been sat in my solcitors inbox since last weds afternoon, not looked at, and searches not ordered. So another weeks delay.
Safe to say they are now reviewing the contracts today and ordering searches (which can take 4-6 weeks!) and he's promised an update on timescales as apparently when they order the searches they get an indicative date they'll receive them by.
He said if everything is staightforward, end of July completion is still feasible. FIngers crossed!