I thought solicitors were supposed to write you an engagement letter setting out a summary of the work you have instructed them to do, the likely costs and the basis on which costs will be charged, complaints procedure etc. If you have not had anything like this ring the Law Society and ask them whether it is a requirement.
The fees should be related to the amount of work to be done and should be reasonable. If, once the work is finished and you are invoiced, you consider the charge is too high there is a procedure for you to challenge it - but you have to pay half the bill before doing so. The Law Society could give you more info. but this is not relevant until later on.