Heated seat retrofit- relay?

[Johnwindwood]

Guys
Have retrofitted heated sports seats to our 1997 M44. All wiring present and connected to the seats, switches fitted and connected.
Logos light up when panel lights are on, but I get no response from the switches when activated-they don't light and the seats don't heat.
Both fuses (4 and 23) are intact. It could be a faulty switch, but it would be a big coincidence for both to fail.
Am I missing something? Is there maybe a relay I don't have?
All advice greatly appreciated!

 

[Johnwindwood]

Just got an answer elsewhere but will leave the thread here in case it is useful to others. Yes, a relay is required-pale green the same as the horn relay and fitted into the port directly next to the horn one. Heaters now working but one switch faulty so on the lookout for another.....