Strideup capital tax on banks interest

السَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللهِ وَبَرَكَاتُهُ
Need some advise please, i currently own a flat but i am currently pursuing a semi detached house with strideup. I am not selling my current property and planning to rent it out.
My conveyancer has added the note below

"Please note, we are not authorised to provide tax advice and therefore recommend you liaise with your Tax Advisor or Accountant in this regard.

You should, in particular, take advice on the tax consequences of entering into this transaction, because you are selling your interest in your Property, which the Bank will sell back to you over the term of the finance. There is a possibility, if the Property has not always been your principal private residence, that you may realise a capital gain which, depending upon your personal circumstance, could result in you incurring a tax liability."

This purchase will be my main residence and the current flat will be used for rent purposes only.
Will there be a problem with capital gains tax?
I am paying the sldt for additional home which is about 400. 5 plus 3 %