The answer to the first question can be conveniently found by pondering the "Big Mac Index" which "The Economist" thought up back in 1998 "to make exchange-rate theory a bit more digestible" Or in other words to more easily illustrate purchasing power parity (PPP) between two currencies than simply comparing different prices for a cup of tea which brings in so many other factors like the quality of porcelain or polystyrene used in the cup and the length of time the leaves are dunked even before considering the many different types and costs involved in the shape of diffusing teabag employed.

However if you examine the nutritional analysis provided by the Big Mac manufacturers you will soon notice that all Big Macs aren't the same. A US Big Mac gives you 540 kcal whereas ostensibly the same burger sold in Europe only offers 493kcal. The European or British Big Mac has nearly double the salt, less weight, less protein and more fat.

The average Big Mac in the USA costs $3.57. Thus we can see that the average minimum wage worker may now afford to buy one Big Mac an hour with enough left over for a large fries and drink, perhaps even a cup of tea. Whereas the average Briton who enjoys the top range of minimum wage at £5.52 an hour is charged £2.29 for one Big Mac and would have to beg (or menace) 6 new pence or half a shilling from a passerby to make up the price of 2 Big Macs in one hour. However this only applies to minimum wage workers aged 22 years and older. For as you know and need not this article to remind you, HM Revenue & Customs applies a development rate of £4.60 per hour for workers aged 18-21 inclusive and allows £3.40 per hour for all workers under the age of 18, who are no longer of compulsory school age. This is usually taken as applying to the sort of kids you can't compulse into going to school but whose knife skills or street wisdom is not up to par for a earning a living through dealing, ducking, diving or motors.

the Big Mac PPP index page :-
 http://www.economist.com/finance/displaystory.cfm?story_id=11793125
about the index  http://en.wikipedia.org/wiki/Big_Mac_Index
about my using the word Big Mac®™ : Big Mac®™ is a registered trade mark for a food substitute which is judging by the nutritional analysis more likely to kill Europeans & Britons than North Americans.  http://en.wikipedia.org/wiki/Big_Mac

the UK HM R&C minimum wage page
 http://www.hmrc.gov.uk/nmw/

Here's a link to "minimum wage by country" from Wikipedia  http://en.wikipedia.org/wiki/List_of_minimum_wages_by_country
Here's an article exploring the differences in minimum wages across the states of the USA  http://money.cnn.com/2008/07/24/smallbusiness/state_minimum_wages.fsb/index.htm?section=money_latest
here's the original wikinews thing which got me thinking  http://en.wikinews.org/wiki/Minimum_wage_in_United_States_increases_to_%246.55

Here's a curious suggestion from the "small biz" association of the republic of Ireland who want to kick-start their economy out of recession fears by cutting the minimum wage by 1euro an hour :  http://www.finfacts.ie/irishfinancenews/article_1014196.shtml

That last repulsive lobbying stance reminds us of how "minimum wage" though almost always practically set by corporations such as Walmart and Mc Donalds both at worker capitalist income and expenditure level, the benchmark so determined affects wealth perception and wealth creation aspiration by small business owners and their collective groupings worldwide.

I can't go on.
sorry.