If you are genuinely after a Macbook but can't justify the full cost and are willing to make, in my humble opinion, a small compromise then read on...
There is no big secret. The compromise is that I got the US version instead of the UK which was shipped from the UK also. The latter is the most important. The last thing you want is to be stung by import tax/duty charges.
The difference from a usability aspect is that the keyboard layout is slightly different. There are around 5 keys which are different, the most noticeable of them being the return key. The socket for the power adaptor is a US type but you can easily get a US -> UK adaptor.
Where the heck is the £ key?
Ok, this was literally the only nuisance and real dilemma I had using the US keyboard which was that it had no £ sign on the keyboard. Considering us Brits regularly (obviously) use the pound key I quickly googled and found that even though it doesn't display on the keys you can get it without changing the layout on the setting. Only reason I didn't want to change the layout was that I wanted the text on the keys to match what it output. You can quite easily change these settings to the UK which will make it match a UK keyboard, probably makes sense for someone who touch-types etc.
I did change the dictionary of the keyboard to UK version so I don't have to use a z everywhere instead of s. Can you visualise what i mean... :)
On the Macbook you can actually get the pound key even though it is not visible on the keyboard. All you have to do is, instead of holding down the option key you press the shift + 3 which is what I am using to display £.
Tips on how & where to buy
The first tip, please please please, if the seller (especially on sites like eBay) has a "submit best offer" then make sure you give a low price to start with. This clearly means the seller has some give in the price. You can then negotiate to something you are both happy with. I have seen many people get accepted for the spec above on offers between £1499 to £1600.
In the links below I have done the leg-work and given the details on the Oct 2013 Macbook Pro Retina with dedicated graphics but this is just if you are after the same one. If you want a different model then the same idea can be applied with all, Pro and Air, in all sizes.
eBay MacBook search - (cheapest) Rearrange by price and set Item location to UK only.
Apple ME294B/A 15-inch MacBook Pro with Retina Display (Intel Quad Core i7 2.3GHz, 16GB RAM, 512GB HDD, Iris Pro Graphics, GeForce GT 750M 2GB, Mac OS X) - (Currently cheap at £1599.99 but does vary depending on stock)
NEW EU USA AUS UNIVERSAL TO UK TRAVEL ADAPTER 3 PIN POWER PLUG UK SELLER
In the video below I describe what the differences are exactly, and how much of a compromise it actually is.