iv now owned my rs for a year and in that time it has never run!!

i bought it cheap as a non runner on the basis that it needed the metering head adjusting/replacing!!!
iv since found that was a massive lie!!

and have spend the last few months rebuilding it as it was a complete state!!

iv just gone for a standard-ish rebuild to get it running but now the engine is back in and it wont start

when i turn the key i just get a click.(relay click)??
i thought it was the starter so have replaced that -still no joy
i get ignition-handbrake light headlights etc but when i go to crank it just clicks!!
timing is ok and turns over by hand,
starter and alt are both being fed
fuel pump is buzzing ....
where do i start??what else can i check??
any help greatfully received as its driving me mad just sitting there! i want to see want it drives like!ready for summer!!
thanks mike