There is I believe considerable confusion surrounding the titles that some people use in connection with their trade. In Britain there is no clear distinction between the capabilities of people who use the title's of 'engineer', 'mechanic', or 'technician' The title is used more to denote a persons position of seniority in an organisation rather than an expression of their proven abilities.
In many countries there is a clear ladder of progression and the title differentiates between the grades in terms of qualifications, experience and scope of work. The title of Engineer is often only bestowed after extensive evidence has been gathered, and it is revered in the same way as Doctor, or Professor etc.
In the context of UK caravanning, I fell the following differentiations could be appropriate:
Apprentice
This is an employee who has no recognised engineering qualifications but who is working and studying towards achieving them. Usually under the guidance of a recognised trade body that sets the agenda. They will work on the maintenance and simple repair of caravans under supervision.
Assistant Technician
On attaining the core qualification they will have one or more of the Caravan Gas, electrical and Water Systems, body and running gear specialities to a minimum competence. They will work unsupervised on basic caravan maintenance and simple repairs using standard spare parts within the area of their competence. If they wish to progress they will continue to seek further skills and competencies.
Technician
Time served and multi-skilled, working on maintenance and simple repairs using standard parts. May work solo or could manage a team of Assistant Technicians
Mechanic
A 'Mechanic' will have an extensive range of relevant skills and competencies. A working knowledge of the necessary regulations. They will be responsible for a workshop and any technicians/apprentices. They will schedule work loads using the relevant skills of their staff, and be capable of assessing more complex repair jobs. A Mechanic will be cable of recreating missing parts or assessing the suitability of alternative components. A mechanic may be self employed, or be part of a larger organisation.
Engineer
The title 'Engineer' has greater implications and should be used for people who actually manage to convert concepts into into realities using process and design and engineering skills. A working knowledge of how to apply Standards and Regulations to new circumstances.
A self employed mobile servicer should be titled a 'Mobile Caravan Technician' and they will be able to complete the essential service features, and basic checks. But for more complex work such as water ingress repairs, a 'Mobile Caravan Mechanic' grade would be more appropriate.
Whilst an 'Engineer' would be able to do all this it would not use their skills to its best advantage.
I stress this is just a personal view on the subject and it is probably incomplete, and not directed at anyone. Whilst I think it would help to differentiate skill levels to help customer understand the capabilities of businesses, I realise that as a result of UK's lack of clarity in this area there are many anomalies.