So two days ago, I get back from dropping the kids off at school to find that there's a large wet stain on the ceiling of the hall. The carpet in the bottom of the boiler cupboard is sodden.
Conclusion: the boiler is leaking.
Our old monitor seems to be on its last legs, so I've just been to Scan's website (from where, >10 years ago, the now dieing monitor was bought) to replace it. Found one I liked, then tried to pay for it. Unfortunately, like most online merchants, they've been bullied into implementing 3D secure (aka Verified by Visa/MasterCard SecureCode).