mk1, mk2, scirocco and corrado front seats all fit, as do height adjustible polo mk3. mk3 seats fit if you swap over the old cabby seat base frame also.
the slider issue depends on the age of the cabby, in about 84ish they changed to the MK2 side which means later seats are a direct fitr, if its earlier than that then only mk1 items are a direct fit. either way if you fit the wrong type seat the only issue is the slider wont work, you may also be able to swap the cabby fdrame over to the new seat dependign on what it is. if its a pre-90 mk2 or MK3 polo then the frame should swap, cabby frames wont fit post 90 mk2 seats or scirocco/corrado.
another option is to swap over the slider handle, easy with a little trickery under the seat. however if the height adjust handle is on the front this wont work as the handle is where you want the slide lever to be! You can get height adjust bases with the handle on the side though, these are perfect for the swap trick.
