Replace RTS1 with BHT-6000 GB thermostat

[itslougher]

Hi all, I have a Worcester Greenstar 24i and 250lt water storage tank. On the ground floor I have a Drayton RTS1 thermostat which isn't working and I want to replace with something a bit more modern. I have just received a BHT-6000 GB thermostat which I thought would look good. The Drayton only has 3 wires and 1 earth but the BHT appears to need 4 wires and no earth.
Can anyone advise whether the BHT does require 4 wires please.
If this is incompatible can anyone advise on a more modern thermostat that is compatible?
Thanks all, Gavin.

RTS1 thermostat and below that the BHT thermostat

 

[ianmcd]

Its fine it is easy to wire

N=N
L=L
Existing wire in 3 to 2 on new stat
make a link between L & 1 on new stat