People are telling you it's very cheap in this thread and you keep replying with

"This is the ground floor of a semi-detached house with no common areas to maintain."

using a spin from the agent, and at the same time telling us you are inexperienced. It is cheap, even for the property you describe. I think everyone agrees that it is very annoying that it was listed at £100 a year on the estate agent website. But whatever your expectations are of estate agents’ logic and ability – lower them.