I'm here in the States, I've seen these advertised from that side of the pond,
I've never seen one in person, or used one, But I believe they are to use a UTH in your situation, Just something you might look into
"The Viv Exotic Heat Mat Holder has been specifically designed to enable heat mats to be used safely with wooden vivariums. It incorporates twi layers of glass so that air can circulate across the surface of the mat to reduce the risk of overheating and thermal blocking. For use with the Medium sized Exo Terra Heat Mats."
https://www.reptilecentre.com/vivexo..._p31511970.htm