Mrs P had a lloyds duo MasterCard purely for the air miles, but I don't know if they still do that. She puts as much as poss through her Amex ie Amazon, eBay etc, and has this has paid for many a holiday in air miles. I am not that organized.
have mbna combined visa/amex - it's straightforward and they give a generous credit limit from the outset - my 'go to' card for medium purchases (e.g. group ski trip for £15k)
Have applied for the amex gold