CIBSE Members operate in a highly professional manner governed by a Code of Conduct. When engaging a CIBSE member you should make clear what the job is and listen carefully to the advice given.
In the early stages of your work your building services engineer may put considerable time into surveying your property, assessing your requirements, researching appropriate solutions and preparing calculations and drawings. Work done before a formal contract is issued will often be billed on a time charge basis and you should ensure that you understand these charges and have discussed the estimated amount of time that will be spent. You could also agree a lump sum.
CIBSE recommends that you agree this early work in writing (you can do this by email), even if you are working through an architect to avoid any misunderstandings. If you are working through an intermediary such as an architect or other professional you should ensure that you have discussed to your satisfaction how charges will be made and paid. In some circumstances a charge will be made for an initial meeting.
The role of the professional engineer, even in the early days before a formal a contract is to provide professional consultancy which is not the same as providing a simple quotation e.g. for building works. A visit to the property may only be a small proportion of the work done for you.
CIBSE does not publish standard contract documents but many building services engineers are members of the Association for Consultancy and Engineering which represents the business and consultancy interests of engineering industry in the UK.