Marty, I've never visited this store specifically but there's the
Widescreen centre in central London, but from memory pretty much any of the other retailers are way out of the city, no doubt because of the cost of real estate. Telescope House isn't far out (maybe an hour?) but it's not "in London".
B&H usually stock a fair amount of stuff, but I don't recall how much astro gear was on display. I just remember the vast array of photo gear. Adorama is another NYC based retailer. If you have an ongoing relationship with a US-based vendor, they will sometimes ship to you when visiting, but if you just order cold then they usually refuse because of the instances of credit card fraud.
Out of the two, you'd almost certainly get better pricing in the US, just remember that you'll pay sales tax on top of the price you see, whereas in the UK it's included. Depending on what exchange rate you get though, the savings might be marginal unless it's something you just can't get in Australia.
