Sale of Goods Act = Your Rights
Sorry to contradict Alien8n but your statement "Under the Sale of Goods Act all goods are covered for 6 years anyway." is totally incorrect. The 6 years refers to the limit for bringing a court case in England and Wales (its 5 years for Scotland by the way as they have a different court system).
Goods are supposed to last "only needs to last as long as it is reasonable to expect it to, taking into account all the factors". Factors might include the materials the goods are made of, how much they are used, the environment they are used in. So for instance a set of cutlery should last a number of years, while a mobile phone might have reasonable lifetime of just 2-3 years and a paper/plastic kite might have a reasonable lifetime of just a few months.
A complex and expensive consumer electronics item used indoors, used with approved software / games (i.e original not copied games) and without any unauthorised "mods" to the hardware, and which is used a reasonable amount of time each day (lets say 3-4 hours per day) should have a reasonable lifetime of several years.
Sony's contention that they can get away with a one year warranty is facetious.
You should note that any claim you may have with a defective unit is with the RETAILLER (ie. the shop you purchased it in) and not the MANUFACTURER. You have a legal contract with the retailler and they are obliged to accept the laws which include the SALE OF GOODS & SERVICES ACT.
You should always retain your RECEIPT - your proof of purchase - and if possible retain any manuals (although its not necessary to retain the original box beyond a short period).
Take the item back to the store where you purchased it and ask to speak to someone. Its advisable to have everythign written down (preferably PRINTED) so you can detail the problem and also have a copy of the information here
Sale of Goods Act (UK GOVERNMENT WEBSITE)
You should not have to resort to it, but if you have reached the store manager and still cannot resolve your problem then take your goods away (never leave them in the store unless you have a written undertaking to resolve the issue to your (not thier) statisfaction). Then take the problem up with the Customer Service team at the company's head office.
Additional information can be found here
The last avenue is a Small Claims Court action. You should read up on this separately.
In general you are not obliged to accept vouchers, or a repair. Further you should be wary of acepting a repair as this may amend your rights at a later point.
You should of course note that the information above is pertinent to England & Wales (Scottish legal system has different procedures) and that you should seek legal advise if required.