Thermostat wiring confusion

[David W]

I am swapping my old Timeguard dial stat which is 3 wire for a Honeywell THR870CUK digital programmable stat. The installation instructions are not the best so need a bit of advice as which wires go where, I have included a picture of the old stat wiring and a wiring diagram and connections of the Honeywell, any help would be appreciated
Thanks

 

[ericmark]

Use A and B only with wires with the brown and black wires the grey is not used any more.

 

[Echo the husky]

Use A and B only with wires with the brown and black wires the grey is not used any more.

So put the grey wire in a small connector block and tuck it safely out of the way. The same with the earth wire in a separate connector block.