Has anyone sub-let their spare room in a property they own?

[FairTurtle]

I'm guessing I need to inform my mortgage lender? As well as contents/buildings insurance, etc?

I'm not sure if you do if it's just a lodger, but I could be wrong. I've done it but not with mortgage.

I don't think you do need to with a lodger, same as if a partner moved in to your house you wouldn't tell the bank

But yes add their name to the insurance

Not for a lodger.