Thanks so much for getting in touch and can I begin by sympathising with you; you have unfortunately found out the hard way that a good solicitor is key to a smooth property transaction.
It's why I recommend that both vendors and buyers should begin their property journey with their solicitor (and yes, a solicitor who is well versed in the Northern Ireland property market really is a must!).
I'm glad you came to me before jumping ship, particularly given the stage you're at with your purchase because while you absolutely can change your solicitor at this point - it could impact your mortgage offer and here's how:
A mortgage offer states the name of the solicitor acting for the lender (i.e. your solicitor - they will be handling the money being paid out by the lender to carry out the purchase on your behalf).
So if you want to change solicitor, this affects the mortgage offer from a legal point of view. A lender will not automatically transfer its instruction to the new firm you opt to work with. So, in this case, you will need to contact the lender and ask them to issue a new mortgage offer in the name of your new solicitor.
Your letter doesn't go into detail on the reasons why you've gone off your current legal rep; there are indeed horrendous 'quick buck' practitioners out there, who don't actually understand the conveyancing process and simply do not operate effectively.
That said, there are also poor estate agents - if you're frustrated by delays, are you sure that these are being caused by the actions of your solicitor, or could they be caused by the agent or other party?
If you haven't already, I would very much recommend a frank conversation with your solicitor to address your concerns. It may be that they are blissfully unaware that you are unhappy; maybe they are unused to looking after first-time buyers and are assuming a certain level of knowledge and understanding on your part. An honest conversation may answer your queries, allay your worries and frustrations, and open up blocked channels of communication.
If there's more to it and you want to have a more in-depth chat about this, just drop me another line to firstname.lastname@example.org and we'll have a coffee.
If you have any questions for me, email email@example.com, or I can also be found over on Facebook, Twitter and Linked In - happy to chat on any of these channels. Keep an eye on the socials for my new series of videos chatting about my Investment Properties of the Week. These are also coming soon to this site; watch this space!