I can't believe that NOBODY has pointed out the bloody obvious here...
Forget the sodding TV, if ANYBODY working for me (sorry, Logistics is my forte) ordered a year's worth of stuff in one go, particularly if it tied up £5k of my own bloody cashflow, my boot would hit their f**king arse before they knew what to bloody do! As any astute businessman knows, cash is king, and available cash in the bank is the be all and end all. I could potentially understand if this was something like biro's, or sellotape, but a year's worth of either of these doesn't cost £5k unless you're a VERY large business.
Forget the TV (which incidentally is the company's, he was rightly sacked FOR DEFINITE), if you're in purchasing and you fall for the age old tricks of "here, buy a year's worth, we'll chuck a freebie in" then you need to be looking for another job anyway if you ask me! That kind of inefficiency, driven by blatant greed obviously (in the knowledge that he was going to get a TV, and keep it for himself), would not have any place in any company that I had any responsibility for.
This is cut and dry, honestly, no 2 ways about it. Even if he gave the TV back, it's still intent to steal or defraud. Gross Misconduct, not an employment lawyer in the world who would defend his case I'm sure!