Under EC Regulations all advertised prices must include all non-optional taxes, fees and charges.
The only way Cryanair can advertise a £1.00 fare is if that is inclusive of non-optional taxes, fees, and charges. He does do this, but to do so has to absorb the taxes he pays out of his own pocket.
However "optional" charges includes charges for use of a debit/credit card. Most airlines have one which is free (Visa Electron, MC - Prepaid) but whack you if you use anything else. Since one is free, he doesn't have to include this charge in the advertised price. So his £1 fare is actually £9 since he charges you £4 per sector, per passenger, for using most debit/credit cards. Of course if you have the MC prepaid card your price is £1.
So my idea is that in cases of variable charges (free to £8, for example) the highest charge for a round-trip journey should be included in the price.