Since I've not installed these thing's I'm not certain, but going on what lecc said it sounds like it goes
Timer > MCB > Lights/or other current using equipment
therefor the busbar would have to be cut at some stage to allow for this.
Quote:what rating would be the mcb before the timer, I would guess 6A, is it correct? would rcbo be suitable as we are talking about lighting circuit
for a lighting circuit 6A would be fine, the timer won't use much current on it's own, although the current will pass trough it. An RCBO is both a RCD and an MCB, therefor again it would be suitable, but under normal circumstances you wouldnt be required to have an RCD on you're lighting circuit, you would be looking at £30+ for an RCBO to protect the lighting circuit