Laptop questions about going to Scotland

A client of mine is thinking of taking an extended trip to Scotland.  I'm advising her on a laptop to buy.  I think a lightweight Dell latitude D420  would be good.  I just want to make doubly sure that the existing power supply would work, only adding a plug adapter.  Here are the specs of the three possible power supplies:

                      65 watt Adapter        90 watt Adapter             Slim Auto/Air/AC
                                                                                                Power Adapter (65 watt)

Input Voltage     90-135 VAC /           VAC90-135 VAC /        VAC100-240 VAC @ 50/60 Hz;
                           164-265                      164-265                         DC: 11-16 VDC, 8 A

Additional cost:    none                         $19                                $69

She is not rich by any means.  If all three work, is there any reason to spend the additional $19 or $69?

Then theres the choice of wi-fi cards.  On this model she can get an a/g dual band card for an additional $19.   Theres no N option.  Is this worth $19 more?

Final question, does anyone know if fast Internet is generally available in Scotland?

Thanks,
Al