Standard declarations and questionnaires don't work for service providers as generally they provide a specific function.
Look at what they do for you and draw up something fairly loose and open.
In your examples, most pest controllers give you their service agreement such as 8 visits,4 Field Biologist inspections call outs, follow ups etc. If you are happy with that just get both parties to sign it.
In the case of Fork Lift Servicing, something like the 'service provider will visit and provide preventative maintenance on 10 fork lift trucks 4 times annually and will attend for breakdowns and unplanned repairs as requested by the company. The cost for these services will be agreed by the client and the service provider on an ongoing basis'
Always put in a clause that those attending the site will follow the site rules and will advise the client if there are any risks to personnel and materials from the work that they are doing.
I also like to do a summary of the various service providers, what they do and how you approve them. I will post it later as I will need to hide some identities