I've got to be honest, I only ever had test drive 'issues' at Mitsu, who refused to let me take out an evo without paying for day insurance.
I usually arrive in jeans and a t-shirt, in my car (Focus Zetec, 03 plate... at the time, not been out for any test drives since I got the puma in april I dont think) and I got varying service... Thinking back, these are all the test drive I can remember
BMW-Mini - Cooper + Cooper S testdrive, both accompanied
Citroen - C4 VTS - 1 hr unaccompanied
Ford - ST150 Fiesta, ST170 Focus, Puma (which I bought), Focus TDCi(which I bought), Mondeo Ghia X (which dad bought)
Honda - Civic Type R + s2000 - both unaccompanied, ctr for 1 hour, s2000 for 3 hours
Hyundai Coupe 2.7 V6 - Refused !
Mazda - RX8 'high power' - 1hr unaccompanied
Mitsu Evo - Refused !
Peugeot - 206 GTI 180 - accompanied
Renault - Clio 182, accompanied
Seat - Ibiza PD130 sport - accompanied
Skoda - Fabia VRS - accompanied
Subaru - 2002 WRX Impreza - accompanied
Toyota - MR2 + Celica T Sport, accompanied
Vauxhall - VX220 Turbo - accompanied
VW - Golf v6 4 Motion, accompanied
....
can't think of any others off the top of my head, thats at ages between 20 and 21