Found the following supplier https://www.vehicleclips.co.uk who supply trim clips at a reasonable price. I bought a selection and the following appear to fit the TF, I've given the equivalents from the Rimmer catalogue:
FCP-0572 EUM 10001 mushroom heads behind the seats
FCP-0318 EZM 10011 the white fixings on my TF which hold the T bar in place. They are smaller than the originals and fit more snugly on the mushroom head on the T bar.
FCP-0364 DBP 5563 Loads of applications on the TF
FCP-0009 CYH10001L Unthreaded plastic nut
FCP-0029 General fir tree fixing, I used for the boot carpet
FCP-0603 This one fitted over the fixing which holds the carpet on the top-hat fixing holding the sound insulation in the footwell.
The above is probably not exhaustive but covered the ones I was looking for at the time.