If the certificate is for £2500 + VAT i.e. £3000 - you are entitled to a refund unless the certificate is extended.
However, as you no longer instruct your solicitor, the certificate cannot be extended.
At the very least you are entitled to the £500 overpayment.
The above you know.
As the certificate is limited to £2500 + VAT, the LAA will carry out an assessment even if the costs exceed this amount. If the costs are over £2500 + VAT, the court would carry out an assessment but this does not apply in your case (unless there is an order for costs to be paid by another party which I will assume there isn’t).
Where the LAA is to carry out an assessment the LAA has the power to compel the solicitor to lodge a claim. In their fascinating document “2015 Standard Civil Contract Specification” found here bit.ly/1VUBlex you will see at paragraph 6.33 that claims must be submitted within 3 months of the right to the claim arising (as defined under 6.33).
Where the time for submitting the claim is exceeded the LAA can serve a notice requiring the solicitor to lodge their claim within 2 months. In the event that the solicitor fails, the LAA can disallow the amount of the financial interest of the assisted person (paragraph 6.35 refers).
The purpose of this provision of the Contract was made in order to limit delays in Agency being able to account to legally aided clients for monies owed to them or, in the case of revocation, to prevent the Lord Chancellor’s position on recovery from the client being prejudiced (Legal Services Commission v Rasool  EWCA Civ 154).
So, it seems that your solution is clear – write to the LAA quoting paragraph 6.35 of the 2015 Standard Civil Contract Specification and say that you are and will continue to be prejudiced until the solicitor files a claim for costs.
I have already brought to their attention LSC v Rasool case along with another example and the response I received was the following.
"where a position has been prejudiced due to the actions of the solicitor we may refuse payment however that is not the case in this specific circumstance"
I have 10 or so letters here from them all stating the same....they understand my frustrations, nothing they can do, there are no set timescales for the solicitor to have to submit the bill to court for assessment etc etc.
All I want is the overpayment and I think after 4 years there should be something I can do about this but it appears there is nothing anyone can do!
The LAA is limited by the experience of their staff. Personally I would give them chapter and verse and insist that they invoke a time limit for submission of the solicitor''s claim in accordance with paragraph 6.35 if the 2015 code.
You could back this up with a warning that if they fail to abide by the contract specification and by the findings in LSC v Rasool, you will issue a claim against the LAA for recovery of monies paid by you which are over and above your liability to the LAA.
If you did put them on notice in this way, you can head the letter ''Notice of claim against the LAA'' or similar.
If you do follow this route you should be prepared to follow it through and issue a claim which would cost around £35 or so - all of which can be done online.
It is worthwhile visiting the CAB for assistance to ensure that you cover all bases.