If it's advertised as HD, yet isn't, then it sounds like the retailer could perhaps be in breach of the Sale of Goods Act & the Trade Descriptions Act. Depending on what was actually stated, & how it differs...
Lots of v v useful Sale of Goods Act info:
http://www.dti.gov.uk/consumers/fact...page24700.html
What model LG is it? And what exactly were Tesco advertising it as?
---------- Post added at 22:48 ---------- Previous post was at 22:45 ----------
Also well worth contacting these:
http://www.consumerdirect.gov.uk/
http://www.tradingstandards.gov.uk/
Always very helpful.