Hi,
TPS is to the left of the throttle body, opposite side to linkage.

Plugs at 0.65 are too small for a stage 1, go for 0.7 - 0.75 (Stick with .65 for 25psi)

Best plugs for a stage 1, price wise are std esc cos AGPR 12PP8.
Performance wise, go for the NGK9 at around £65 for stg 3 and above cars.

Cold running issues are VERY common on cosworths and can be down to a lot of different things unfortunately, but start with the above.