if you google potterton, you will be able to gat a set of instructions / user guide free from the potterton boiler company although i dont see why you should have to chase around on your agents behalf.
i know this manual is free as i got one for my sons boiler, powermax 140, and use to service his unit. i don,t know what the old fish smell is about but i would insist on a safety check asap. my sons unit is in a compartment (a cupboard with a door) in his bedroom and i check his unit regularly, especially his flue which rises through his loft, with a telgan i borrow from a mate at BGas.
because the boiler has a poor reputation i bought a carbon monoxide detector to monitor for any potential leaks.
i assume you have a copy of the last safety check on the boiler which your landlord is legally obliged to supply you with, in writing?
it sounds like you need to be firmer with them, for your own peace of mind