To be honest, for £700 you are not going to get a lot (that means nothing). A 14 n cruise on a 'decent' line will cost around £999 if you wait for the special offers, and this is without spending money I'm afraid.
Hi try Fred Olson or click the Blue Standby Cruises on this page to the right of your Question they are discounting quite a lot and you may find what you want?
It depends on your age range are as to which company to look at, b whether you want a more formal dining experience or informal and c where you want to go. The blue stand by is a good idea. The canaries will still be hot then but some places will be cooler. For more informal try Ocean Village, Island, for a mixture try Royal Caribbean, Princess. For more formal try Cunard. You do get what you pay for! If you think carefully about the abc you will get what you want.