I'm not a GP, I don't know 100 % on any topic, and good advice and information has been posted already .
Your profile says you're married to a beautiful filipina so chances are she's healthy ! Therefore I would be cautious about ANYTHING " over the counter " ( OTC ) unless it's really necessary. For good reasons, it's true you can't obtain antibiotics OTC.
Common colds are self-limiting, and no specific treatment is usually needed ( or effective ).
Flu is different, vaccination is recommended for those at risk, but drugs such as " Relenza " are not routinely used for treatment - they don't cure anyway.
OTC antihistamines may be helpful for allergies like hay fever.
OTC painkillers such as ibuprofen and paracetamol may also be useful for a variety of aches and pains.
There's a huge amount of information on the internet as you know. Here's my summary :-
Don't buy ANY combinations of drugs which have trade names like " Neozep " ( or dozens of similar combinations available OTC in the UK ).
It contains paracetamol and antihistamines. " Biogesic " also contains paracetamol and antihistamine(s). " Medicol " is ibuprofen alone.
It's best - and cheaper - to buy what you need under the generic name. Use the correct - but minimum - dosage. Paracetamol is good for mild to moderate pain and fever, but
may have side effects.
Non-steroidal anti-inflammatory drugs like ibuprofen are effective for pain and inflammation relief, but can have serious side-effects, such as stomach ulcers. Use with caution for no more than a few days ( and not if pregnant ). See your doctor if symptoms persist.
Antihistamines - for various allergies - are also effective but have side-effects !
Medicine these days should all be " evidence based " - any treatment should be proved to be effective and as safe as possible. The same should apply before spending money on OTC remedies - know what you're buying and what you're treating .