are front and rear component speakers 6.5" and do you need adapters to put them back onto the doors?

The fronts are, but you're limited to a mounting depth of approximately 6cm. You need a spacer. Come people use the Golf adapters, but MDF rings are a better option in terms of sound quality.

Rear speakers are usually 10cm in the rear deck (side of the parcel shelf) with a tweeter in the door. I wouldn't worry too much about the rears, they're more for the benefit of rear passengers.

The rear bass/mids are 10cm ish with a square mounting plate, the front and rear tweeters are the same size.......I just uprated the rear mid/bass as the boot acts like a sounding box.....anyway my 4 x 50w headunit has got that many custom x-over settings it's not true!!!!.....and if I'm really driving the music goes OFF so I can hear the engine......

whart size are the tweeters in the car then?

I think the tweeters are 1". Think it's a standard size anyway.