You will get what you pay for when it comes to a Liquidator. I know from past experience that around 8k is an appropiate for the work involved in this case.
Many armchair liquidators do not realise that a signficant amount of time must go into the investiging the insolvecy of the Company and a comperhensive report must be filed with the Director of Corporate Enforcement.
Currently, insolvencies are boom time for accountancy practices and I'm sorry to say like in the boom time with builders, there are cowboy liquidatiors out there who will charge a fee and do nothing.
When you agree that you need to go down the liquidation route, you need someone with experience, liquidators do have various obligations under Company Law some of which are not being adhered to by many 'cowboy' liquidators.