It seems that BKC battlegroups are based according to certain rules re base size etc, but I can't seem to find them anywhere in the rulebook or on the website.

Can someone please fill me in?

Cheers,

Aart

BKC I had some base sizes, (BKC II doesn't) but for the game it doesn't matter too much what sizes you use.

My stuff is:
Infantry 50 x 30mm,
Support weapons (Mortars, MG) 30x30mm
ATG, AA 40x40mm
FAO 1p coin, HQs 2p coin CO 40-50mm square
Vehicles unbased, unless they're small (bikes, jeeps etc)

Thanks, Dave 

Cheers,
Aart

I don't think it makes much of a difference so long as the opposing forces aren't too dissimilar. I use different basing from my friend and it all still works

I use,
Infantry 40x20mm
Support weapons 25x25mm or 40x20mm
ATG and bigger 40x40mm
Tanks and transports etc 20x40mm or 30x40mm Depending on size
FAO 1p,
HQ 2p
CO, 50x50mm

Generally whatever is needed to fit the models.

I use the original bkc basing wich is::

infantry/support 50x25 (in bkcII it is suggested to bring support like mg' mortars etc back to25X25 bases, but i keep 50X25 with two mg's/mortars to a stand, i find this looks more appealing)
recce/transport 50X25
fighthing vehicles and spg's 50X30
artilery/anti tank/ FAO / FAC /HQ 40X40
CO 50X50

But as everyone says, as long as you are consistent over both sides it's all good.

Thanks all of you. My worries are over. 

Cheers,
Aart

Infantry 50mm x 25mm
Infantry Support 25mm x 25mm
ATG either 25mm x 25mm or 25mm x 50mm dependent upon size.
Artillery Support 25mm x 50mm
CO 40mm x 40mm (I think)
HQs 25mm x 25mm
Recce Infantry 2p coin
FAO & FAC 2p coin

I think that covers everything...

Yep, I agree with all the above. My infantry are based on 30 x 20mm, so that I can use them for FOW as well. I don't base vehicles at all and it all works seamlessly.

My infantry are based on 25mm by 25mm bases so I can also use them for crossfire, you can use anything you like.

Crossfire? Bit harsh on the paintwork I feel.