Dell retorted that the price of £349 included an "upgraded service package", which customers could unselect if they so wished. They claimed it was "industry practice" to automatically upgrade the service option.
The ASA has upheld the first complaint, but rejected the second because there was a note on the site that told people to downgrade the service option in order to get the £299 price. I haven’t actually seen this page but you can bet that the note in question was in a pretty small font.
Specifically, it breached CAP (Broadcast) TV Advertising Standards Code rules 5.1 (Misleading advertising), 5.2.1 (Evidence), 5.2.3 (Qualifications) and 5.3.1 (Accurate pricing).
In a nutshell, the findings of the ASA were that Dell's online practices were clear and acceptable, but that the TV ad was unacceptable. The ASA ruled that the ad must not be broadcast again in its current form.