Which central coast?

I'd head south to Sydney if I were you. It's possible that you'll find
a cheap and/or well stocked place on the (NSW!) Central Coast, but
with a smaller customer base and less demand I'd be surprised.

Best places that I've found:
1/ If you know what you're looking for and don't want any advice or
service, try CCC Camera House at 416 George St Sydney (02) 9232 4500.
I bought my 24/105 f4L from them at... quite an astounding price,
actually. I've also enquired about some other lenses that I've been
thinking of getting, and they've had each one in stock save one (Which
they said they'd be able to get in about a day or so if I ordered it,
incidentally.) I emphasise; they pare their prices to the bone and are
willing to haggle; advice and service are the trade off. If you don't
have cash (or Visa) in your hand, they probably won't want to know
you. For serious players only.

2/ Similar, but the prices can be flaky (as in sometimes high,
sometimes low and you need to compare other places first), G & V
Imaging at 400 George St Sydney, (02) 9221 8899. (Corner of George
and... King, I think it is.) Like CCC, they have an Aladdin's Cave of
Canon lenses to drool over. (It's located on their first floor level.)
I bought my very first digital from them (an Olympus 1.3 megapixel...
ah, memories) for, at the time, one of the best prices in Sydney.
However that was quite some time back now, as you can guess, and I've
been very unimpressed by their prices of late. They're often little
less than RRP. However you said "range", not "price", and range they
have. They were the only place in Sydney that I could find a
particular Manfrotto tripod that I was after a few weeks ago.

3/ Foto Riesel Camera House at 364a Kent St Sydney (02) 9299 6745. I'd
have to say that these guys are my favourite, and I know some pros who
swear by them. They're not always the cheapest, but they'll come close
and the people who work in there give the impression that they love
photography more than your money. (They probably like the latter as
well, but with the first two places I count my fingers when I come
out. Though I mean that in the nicest possible way, to the extent that
there IS a nice way of saying it.) With Foto Riesel, I may pay a small
amount more but generally come out of the store with a better feeling
about the purchase... except... well, lets face it, when you have a
new lens or other toy to play with you're feeling pretty damn good
anyway. 8^> As with the others there's a whole display cabinet of
Canon lenses and you'd probably find what you're looking for.

If I'm in the market for gear I usually ring around other places as
well, but always end up at one of these three... and usually CCC or
Foto Riesel at that.

It may be an idea to call them first and see whether they have the
lens that you're after, assuming that you have some idea on that.

Hope this helps.