Hi there,
Some good information so far as well as links. I'll take it a step further for you and for anyone else who sees this thread.
The 'major' outlets as mentioned so far are the most well known retailers. Richer Sounds is an excellent reputable and well known in the discount area of retail. As a large percentage of all sectors of UK goods are priced significantly higher than other countries, and in this case and website, to the USA, I along with many others look to find places which offer the very best possible pricing. To this end, there are places to look at to get as good a deal as you can.
Some of my favourites are :
http://www.laskys.com/ (Comet is the store in the shopping centres, in turn 'Comet online' is where they offer discounts. Laskys is owned by Comet and they operate entirely online, and their pricing is substantially cheaper than Comet high street shops) I've bought a Dishwasher, Hoover and a set of DECT cordless telephones recently, arrived within 36 hours of ordering and saved good amounts of cash)
http://www.ebuyer.com/ - well known online for excellently priced goods, also will cover PC and computing as well as other household goods.
http://www.dabs.com/ these guys have been around for quite a while, although lately i've seen less of their advertising.
http://www.play.com/ - often have some excellent pricing and are a very close competitor to Amazon. I've had a 26 inch Sony LCD off them recently, and again - excellent service and smooth to deal with.
http://www.hyperfi.co.uk/ - another well known long established Audio products discounter - very similar to richer sounds.
The above are ones I look at often when it comes to comparing pricing. Now that I have less time, I can't do what used to be my favourite choice of price checking - which was to go to Tottenham court road in London and play off the dealers pricing comapared to one another. This place is where you get your electronic's at the best possible pricing, however now that the internet is here, the pricing differentials are much closer. Still worth checking out though, as the shops would change often due to competition, the only one I can think of who've been there all the way through are Micro Anvika -
http://www.microanvika.com/default.asp If you're confident enough, don't forget to check out Ebay - I've just recently purchased a full Celestion cinema surround component system from Hyper-fi's ebay outlet, at a good saving compared to their online website and store price. i think Richer sounds also have an Ebay presence. Make sure you do your research into any other sellers - more often that not, they are reputable (I think seven oaks hifi are on ebay) - just ensure you can talk to them on a geographical landline and that they're power sellers - the potential for bargains here is excellent!
Costco - From my many and frequent visits, I've not seen them selling last seasons electronics models - they've always been current range. There will be sections where older stuff might be around, but I'm pretty sure they'd mark them as such. I beleive Costco's wholesale focus is on current products. When they don't sell, they then sell those items off in bulk to other purchasers where they'll end up in retail stores and/or Ebay.
I am of course assuming you are aiming at getting a best as possible deal. John Lewis do have a good deal for 'convenience' in their marketing strategy, but that 5 year warranty has to be paid for somehow, which is them selling to normal retail pricing. Only if customers ask them to price match lower wil they possibly do so, but considering they 'bank' on most of their customers not doing so, they can achieve their high margins most of the time. For 'peace of mind' then by all means go with JL or anywhere else that offers similar.
One little known fact in UK consumer law is that the commonly held belief of 1 years statutory rights is fact TWO years statutory rights, which eats away at the '5 year John Lewis' warranty. With 'large ticket' items, statistically time to failure usually occurs within the first year after that you can press for unfit for purpose clauses etc - but as your statutory rights actually allow 2 years, your protection is increased. By paying the likes of JL extra for their statistically 3 years worth of extra cover you probably wouldn't need, you're helping them survive! - I guess it's just the way legislation is looked at which determines an individual's evaluation of which way is worth more to them.
My source for the information of the actual 2 years of statutory cover rather than the commonly percieved one year was from a recent article on MSN Money website which in turn linked to a Times article showing this. Please check the relevant consumer law websites to read up on this (I dont think it's changed) and any specifics etc.
Hope the above helps.
Cheers! DtM! West London & Slough UK!