As Gok Wan states, the restrictions on liquids only apply to hand luggage. The details are here:
http://www.dft.gov.uk/transportforyou/airtrave l/airportsecurity/
You can normally take food and drink in your hold luggage as long as it doesn't contravene, for example, rules about the importation of meat or dairy products. Additionally, of course, there are limits on the amount of alcohol you can bring back from non-EU countries.
However, Mountain Dew isn't alcoholic and doesn't breach any food regulations (neither does your confectionery) so you can bring back as much as you like (subject, of course, to your baggage allowance).
The total value of gifts, souvenirs, etc, that you can bring back should not exceed �145, otherwise you'll have to pay Import Duty and VAT. (Your Mountain Dew and confectionery theoretically counts towards the �145 total, although HMRC might ignore them if you only had small quantities).
Virgin Atlantic baggage information:
http://www.virgin-atlantic.com/en/gb/passenger information/baggage/index.jsp
HMRC import rules:
http://customs.hmrc.gov.uk/channelsPortalWebAp p/channelsPortalWebApp.portal?_nfpb=true&_page Label=pageTravel_ShowContent&id=HMCE_PROD_0102 20&propertyType=document
Chris