Thanks again, I will check out the mould situation. Is it plausible that the smell (which manifests when the boiler is operating) could be due to mould?
Thank you both for your comments!
I'm not sure about the presence of MDF - I will ask her to have a look. I don't think it's dust mites (I think the smell would rule that out) but I will suggest the allergy test and have a look at sick building syndrome (I hadn't heard of that before).
I...
First of all, apologies in advance for being vague - I'm posting here having exhausted other options and am well outside my sphere of knowledge. (I've also read the FAQ). I will be as thorough as I can, so please also excuse the length of this post.
My mother, who lives alone, moved into a...