Right, I'll make an assumption, you currently use no.1 on the 103 for your switched live to the boiler and currently have a link between Terminal 6 (L) & terminal 3 in your timeswitch?
To wire the timeswitch and roomstat in series, you will need 4 core cable (3 sheathed and an earth).
Remove the current wire from term 1 on the timeswitch (label it as you will be using it later). the 3 wires on the new cable to the stat connect FROM the timeswitch as follows:
t/s=timeswitch
r/s= roomstat
#.1 on t/s to L on r/s.
#.5 (N) on t/s to N on r/s (N to N).
Link r/s L to #3 (as stated on r/s) on r/s instruction.
#.1 on r/s goes back to t/s and links with the
previous removed switchlive (from term 1 t/s)
These two wires can link in terminal 2 on the t/s wiring (as it's a spare)
Good luck
Carefree
July 2010