Of course you get these in the tropics, but here in the UK adults get 2-3 colds / year on average.
For the common cold, many different viruses cause it, so antibiotics are likely to be ineffective or harmful. Antihistamines and decongestants may help. Vitamin C is likely to have little or no effect. Painkillers and anti-inflammatory drugs won't reduce the duration of the cold. Common colds usually last only a few days, and resting with plenty of sleep is sensible.
Just be careful how much you spend on common cold remedies! Don't buy the "big name" remedies ! It's been shown that supermarket own brands are far cheaper, for the same active ingredients.
Flu is different, much more serious, but also less common than "colds". You won't get "flu" more than once a year! Free flu jabs are offered by UK GP's for people most at risk. These include:
anyone aged 65 and over
serious medical conditions
carers for elderly /disabled people
work with poultry
pregnancy (if not already vaccinated against swine flu).
Obviously being registered with a GP is a priority in the UK, for many reasons, but they won't welcome you in the surgery for an uncomplicated common cold.