Thanks for your replies folks, i decided against doing the alterations myself and got an fully qualified electrician to do it for us. I don't mind doing things myself but when i had no real idea about timer and with it affecting other people thought it safer to just get it done right first time!
I'm looking to replace an existing Electro Mechanical Sangamo Solar Dial timer with an electronic timer i bought from RS-Components (505-9833, MLU2 7 day 1 channel digital timer).
The existing timer has Live and Neutral (Red and Black) wires going in and Live and Neutral (Red and Black)...