Just one other point, Ali.
If (and I emphasise if) you instructed a firm of solicitors to act on your behalf of you as executor of your mother's estate, and you paid them £700 to do so, and they did not act on your instructions, you may be able to make a complaint about them.
But your story is unclear.
What did you instruct them to do when your mother died?
You don't seem to know
- just that your brother told you to do so, but you don't seem to understand what your brother was asking of you?
FWIW I feel sorry for you.
I think, simply from what you have posted here, that you might be being exploited by family members.
I say "think" because you seem to be unable (for whatever reasons) to explain coherently what has happened.
I know you are going to a solicitor.
That is what many others here have suggested.
Again, good luck with that.