first of all, congrats on finally being able to get a job

Hopefully, you will be able to get riding on your motorbike soon
With chuggers & other such related jobs is that quite a lot of people have become pretty worn down by being approached every 10 metres by the street rep of such and such charity that it becomes a bit of a nuisance. As others have said, I will politely say no when asked or simply get out my phone and pretend I'm texting when I am about to pass a chugger/charity street rep but no I would never be horrible like some of the people you described in your OP.
Esaglik, persevere and hopefully the rest of your stint as a charity street rep should go relatively ok