The 1.4 sport is worth a fair bit more than the 1.4rt, well from what I found out when helping someone get another car. (They are rarer for a start, well thats what I found)
I think you should be looking for at least £400 over what parkers gives for a 1.4rt. Below are a couple I found on Autotrader, just for examples
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1997 RENAULT Clio 1.4 Sports Maxim 1997/R, Lavender blue, alloys, s/r, p/s, e/w, r/c/l, immobiliser, drivers airbag, one previous owner, fsh, tax/ MoT November, vgc ono Poole or . . . . (private) more info £3,500
1998 RENAULT CLIO 1.4 SPORT, TRANSAUTO 1998, R reg . 39000 miles, mauve, airbag, alloys, c/locking, e/windows, stereo, s/roof, two owners . Tel: (0118) 957 . . . . (trade) more info £3,799