While it hasn't 100% been confirmed that the same thing will happen in the UK, it appears it's going to get a lot more difficult to get hold of Harry Potter on DVD and Blu-ray in the New Year, as Warner Bros. has announced they will stop shipping new orders of Harry Potter Blu-rays and DVDs to shops starting on December 29th.
At the moment this is just confirmed for the US, but it appears it's Warner's plan to have a worldwide moratorium on Potter. It wouldn't be surprising if us Brits get a little bit more time though, as the plan includes getting Harry Potter And The Deathly Hallows - Part 2 and any box sets off the shelves, and seeing as the last Potter flick doesn't arrive in UK shops until December 2nd, Warner would be giving themselves less than a month to make all the cash they can from the film before they stop taking new orders of it.
Disney employs a similar strategy of pulling some of its classic titles, such as Snow White and The Lion King, out of the vault with brand new editions after being unavailable for several years (with Disney, it's normally a seven year cycle). It is unclear how long this Harry Potter moratorium will last, but if you want a complete matching set of first edition packaging, you've only got a limited amount of time.
I wouldn't expect this moratorium to last that long, and it wouldn't be shocking to hear that Warner already has new DVD and Blu-ray edition planned for the coming years, with more bonus features etc. Indeed there's long been talk of extended versions of the movies being released and 3D versions of all the film are in the works.