When appointing a professional adviser it is most important that he or she should be both familiar with the legislation and have relevant experience in the field. It is suggested that you talk to several practices before you appoint an adviser.
The following checklist of questions might be useful:
How familiar is the practice with leasehold legislation?
How many instructions have they dealt with that require knowledge of leasehold legislation and good practice?
Can they refer you to a satisfied client?
What is the fee structure for the work?
Any competent practice should be able to respond satisfactorily. If not, or if they are reluctant to provide references or be firm on likely fees - go elsewhere.