What Cobber said!
It is completely correct for the TF to have wider tyres at the back than the front.
The definitive guide, on sizes at least, can be found
on David Aiketgate's post here
.
The tyre information is a bit out of date but suffices to say that the TF is allegedly very fussy about its tyres. Current favourites are the Falken Ziex ZE310 or Toyo Proxes TR1. Other tyres have been reported as working well.
Cue lots of people citing their own particular brand of tyres...
I personally have Falken ZE914 on the front and Event Ditchfinders on the back which have served perfectly well for my style of driving but this does not constitute a recommendation!