Laguna II: Replacing front brake discs?

[Jacobite]

Hiya, my front brake discs have some serious grooves in them, with MOT coming up soon I think its time I wack on some new discs and pads.
Looking online I notice there is a range of discs available with different diameters (280/300/308), thickness (26/28) and height(21/27/47).
I'm a little confused with what I do need?
My current discs are 300mm I think, the other measurements i'm not sure about?
Anyone in the know?

[madnoel10]

Renault have a habit of changing not only disc sizes but also suppliers of their brake components. The only way to be certain is to remove a wheel and physically check both the diameter and thickness of the disc and also identify the make of the calipers.
Sadly many a poor mechanic has gone ahead and ordered parts only to find they don't fit and then had to pay additioinal costs for carriage, etc.

Renault ain't the only manufacturer who makes such changes during production.