Cheapest courier

Thanks Peter.

Yes further inquiries reveal that the airline only accepts packages from a company who have an account with them & you have to drop the parcel at the airport. 
I'll be using the link I posted above. 

I appreciate your input guys.

CZ,

Actually USPS will be the cheapest, if you ship directly with an Airline, which will be exceedingly difficult if your not a "known shipper". Since this is an international shipment OP will have to clear customs for the speakers once they reach the UK with all the fees, bonds and paper work that involves. Then there is local transport from the airport to consignee etc. For a one of shipment USPS /FedEx/UPS/DHL certainly would be the preferred choice, since all the above is included in their price.

Best of Luck

Peter

Thanks czarivey & whart...

If you know someone with a DHL account, the rates are a considerable fraction of those quoted as "retail." I don’t really do much shipping, but a lot of buying, so it doesn’t help me too much, but I did get a quote from them at one point, based on a minimum assumption of volume. When I’ve shipped stuff back and forth to Slovenia (Kuzma), I used DHL one way, Franc used TNT, i think, based in EU- I’d get an email mid-day and the courier would be at my door the next day before noon in NY. Crazy!
The key factor, aside from carrier is obviously packing/crating. And the 3d party crating services aren’t always "experts"- based on my limited experience. Good luck!

United airways have best cargo rates for shipping to UK
find out http://www.unitedcargo.com/shipping/productsAndShipping.jsp?name=Quickpak&type=product to provide precise information about your package to get rate.
You should save near half of what you've been quoted by major carriers.

Try delivering directly to cargo airlines so they can be claimed in the destination airport.

Can you elucidate please? 

Try delivering directly to cargo airlines so they can be claimed in the destination airport.

while the government drones work at a frustrating pace somewhere between glacier speed and continental drift.

LOL!

Thanks akg_ca. Indeed you are correct;  peace of mind & reliability is worth the cost.
Although I've found this site which offers excellent prices -- https://www.ipsparcel.com/

I doubt that any potential cost savings (if any) will materialize. It's a competitive marketplace . Your quoted shipping cost is well within the narrow range of comparable shipping quotes for what I have paid in the past.

Let's also remember that the big guys handle their own customs and duty brokerage function. If you chintz it with the "B" team operators, you may easily find your beloved shipment stuck in the backwaters of a very long customs queue before it gets processed. I've witnessed imported shipments stuck in federal customs clearance limbo for weeks on this side of the pond, while the government drones work at a frustrating pace somewhere between glacier speed and continental drift. 

Without  prejuduce to the above, you only get what you pay for.
Engaging a top-tier freight carrier with a backstop of a no-hassle damage and loss policy to handle this fragile gear AND in a timely manner.....is a very cheap cost of insurance to getting it over here in good form and provide you with that ethereal peace of mind.