Badly adjusted clutch
In my experience RHD is more desireable in the UK and thus is more expensive ~£500-£800
S4's were converted by a couple of companies (Bell and Colville - Seaking) and to improve their original sales appeal, the companies, included the hard top in the sales price....
So if your RHD doesn't have one it can help lower the price.
(I didn't want a hard top.. nowhere to store it.. and only use the car when the sun is shining
see... I'm not such a tight wad.... honest
)