Buying Euro's in the UK

A question about : Buying Euro's in the UK

Can anyone tell me the best way to buy Euro's in UK. Just acquired Halifax Clarity for holiday to Crete in August. Should I use this over the counter to buy Euro's as it seems to have the best rate according to this website, or just good ole fashion cash?

Best answers:

• Clarity does NOT get you euros in the UK - only from an ATM overseas.
  Well you can use it in a BdeC in the UK but you will get the BdeC's rates and charges, not Clarity ones.
• Use it to spend and get cash out abroad. There is no need to get Euros whilst in the UK and you certainly wouldn't get them cheaply.