Changing Chainring

I've got, I think, a 52 chainring with a 21 tooth sprocket which can be hard work in headwinds/on uphills. If i swap the the chainring but leave the spider on the BB would this cause any chainline issues?

also, my track nuts are getting worn/rounded/rusty. how do i know what size to get for replacements? on this site it says 10mm but i don't know what is 10mm: http://www.twowheelsgood.co.uk/index.php/product/hubsandhubspares/hubnutsandtracknuts/index.html
it is a suzue rear hub and i think an ambrosio on the front. the old nuts are the cheaper ones without the independent washer

chainring change shouldn't cause probs.

take bike to shop - or track nut to shop - show to bikeshoppus neanderthalis, ask for same, but newer.

Treat yerself to some Dura Ace from Hubjub.

Not really critical on the front, top notch on the back.

http://hubjub.co.uk/etc/etc.htm

52/21 is around 65-66 GI (depending on your wheel/tyre size)

that's already quite light..

What sort of cranks are they? I've got 45T and 50T DA road chainrings at home.

cheers for the advice.
the wheels are standard road wheels i think, the tyres are 700x23. cranks are about 175mm campagnolo (at the lower end of their range).

Changing your chainring won't mess with your chain alignment so go ahead. Check Ribble. I mostly run road rings on my bikes and never had any problems. TA 47/48t rings come in at under a tenner.

you're welcome. anytime.