I did contact the VISA company who informed me I could stop the payments. However, as I had authorised one of the payments via email, the agent could dispute this and eventually get their deposit. So cancelling the Holiday is not an option.

It has occurred to me why I have paid over the odds for this Holiday. The operator moved my Holiday request to the end of my Holiday dates. The dates fell into the beginning of Ramadan and I'm now sure the operator sneakily knew what she was doing. A a holiday before Ramadan would be around £400 more!

How will Ramadan impact my Holiday? Should the agent informed me before booking?

You'll need to provide more information before anybody can help. For example you haven't said where the holiday is to - presumably it is a Muslim country or Ramadan wouldn't be an issue at all but without knowing which country, nobody can advise you because it will vary from country to country and often it will depend on where and to what sort of destination within the country. Also, if you don't name the agent you booked with nobody can help you make sense of their T&Cs and what the implications of cancelling night be or tour chances of getting them to honour any price match guarantee.

SM