£1250pp will get you something, just depends how much spending money you have to go on top for drinks tips,trips and a few treats maybe spa.
As has been said to avoid the posiblity of a downer if you find you love cruises do the stay first.
Allthough a honeymoon is usualy a trip of a life time, if you get hooked on cruises you will do loads over the years.
There are plenty of Med options,, Baltics are very good if you like cities and St Petersburgh could be something that makes a cruise "special"
Caribbean is an option but due to weather you have to be prepared for itinerary changes.
July is also an OK time to do New England with a NewYork stay.
Another must do cruise and would amke a good "special" trip would be Alaska, loads of bargains this year.
The Med is easy from the UK so can become the area you do a lot, if you get hooked, so looking further afield for this special trip might be worth some thought. Also some parts ofhte Med are getting hot by July
I know a lot of people like to do the honeymoon immediately after the wedding, but if there is the ideal fantastic trip some time in July or august or something cheaper in Oct Nov Dec do consider that as an option, the money would get you much better deal in Nov/Dec.