All flights require a change in Europe, usa or elsewhere in the americas. Non stop from Europe means ex-Amsterdam with KLM or ex-Madrid with Iberia, Air Comet Plus or LAN.
Via the US is cheapest option but the government will handle you on arrival exactly as they handle their own criminals. Even if you don't book a stopover, US stopping points on an indirect flight usually means going through immigration.
On this route lastminute.co.uk appears to have better significantly fares than opodo.co.uk at present.
Cheapest fares are via USA. Add 50 pounds if you need or wish to avoid that.
NB No non-stop from UK. Prices are for flights with stop-change in Europe or USA. Duration of stay, less than one month. Low season prices rise to 880 GBP for stays of longer than 3 months.
Non-Stop Direct flights
Flight Time & Airlines: ca. 16-20 [best 1-stop option.] hours. NB No non-stops. KLM via Schiphol-Amsterdam, Virgin via Miami
Rough Best Price 2007 low season: 560 pounds incl taxes etc [810 eur]
Rough Best Price 2007 peak season: 880 pounds incl taxes [1280 eur]
Basically on this route, buying a standard economy return is no no no no way!
How about business class? Bottom Line: Simple answer, only if you've money to burn.
Discount Business Class
KLM via Schiphol-Amsterdam, Iberia via Barajas-Madrid. 16-17 hours. Flights 1 & 12.5 hours. 2120 pounds incl taxes.
I.e. non stop economy + 1240 pounds peak season, + 1560 pounds off season
So, by far the best option for doing it in style but without breaking the bank is a stopover.
The possibilities for stopovers are almost endless with all of the carribean, mexico and much of the USA geographically conveniently on the way. You could even add a stopover in North Brazil, Venezuela or the other South American nations adjoining the carribean to your list of possibles.
The difficult part with many of the possibilities is a flight onwards to Lima. There is a large traffic and therefore large choice of convenient relatively comfortable and competetively priced flights to the Caribbean and Mexico from Europe. Travelling on to Lima is more tricky as most flights are from the major cities in the region not from the beach and holiday destinations