This week: those unavoidable Ryanair charges and the best currency to take on holiday to Mexico

Q. I am fully aware of the various fees Ryanair charges and how to avoid them, but I have just discovered it now charges for online check-in at £6 per person. This is scandalous, since there is no other way to check-in without incurring a charge. Surely someone should be taking it to task for this? Richard Hunt

A. Ryanair, in common with many other airlines, likes to tell prospective passengers about an array of "taxes, fees and charges" that apply to each journey. The principle seems to be that some people are drawn in by the basic fare, and are not deterred from booking even when a range of fees are added. It may also be that some customers infer these sums are beyond the control of the airline.

The Irish airline, which flies more passengers internationally than any other carrier, has a range of unavoidable charges. The cost to the airline of the online check-in operation is only a few pence, but it suits Ryanair to make a charge of £6 per person, per flight. Another interesting fee is the £2 "EU261 levy", which sounds as though it might go into an international fund to compensate stranded passengers under Europe's passenger-rights legislation. It doesn't.

The way airlines dress up their fares is of little consequence to the smart traveller. The only amount that matters is to compare the final quote with other airlines. Ryanair is often, but by no means always, the cheapest airline.

Q. My daughter is off to Mexico – should she buy US dollars before she goes? Chris Gunning

A. If she is one of the vast majority of British visitors to Mexico and staying on the "Riviera Maya" that runs south from the main resort of Cancun: no. There are plenty of cambios that offer competitive rates (certainly better than anything you'd get at Gatwick or Manchester airport for Mexican pesos). Changing from sterling to dollars to pesos would be expensive and unnecessary.

Elsewhere in Mexico, sterling may be regarded as a minority currency – in which case a wad of low-denomination US dollars can be useful.