Dont rate the Recaro ones at all - not the most secure (though they look the biz!)
Depending how big a 4yo he/she is, a Britax Duo Isofix is really good (my 1.5yo has one) - doesnt move at all with Isofix (£120 at the local Halfords) or something like a Graco Junior Plus if theyre a bit bigger (my 3.5yo has one of these!) which uses the seatbelt but fits really well on the Clio back seat, and can be used just as a booster when they get older.
Both are dark grey so match ok!
Matt