I had this and have gone from last week being told "please be patient, another 12-14 weeks" (No chain, selling to ftb, no onwards purchase) to now looking to exchange this week through relentless chasing.
No need to be rude, but end of the day they are professionals and are providing you with a service.
Firstly, check if you've sent everything you need and ask them to confirm they are not waiting for anything from you. Also ask your estate agent to ask other party's solicitor what they are waiting for - try to establish where the delay is.
If it is your side, then ask your solicitor for a list of actions they will be undertaking and concrete timelines for when this will happen - follow up with them and via EA to check this has been done.
If you're not getting responses or they're fobbing you off, you are well within your rights to ask for the escalation process details or contact a senior partner and ask to be moved to a solicitor with a more manageable workload!
You are paying the solicitor and the estate agent a lot of money, don't be shy about demanding attention from them!