Whilst looking at all the usual orlando ticket sites, I came across this offer at viator.com
Universal Orlando® 2-Park Unlimited Ticket - Florida
Enjoy 2 amazing theme parks over 7 consecutive days. Go beyond the screen and Ride the Movies® at Universal Studios« then experience the innovative thrills and cutting edge rides at Universal's Islands of Adventure®.
I've not seen this ticket advertised on other UK websites and it is better value than the usual 2-day/2-park (with 3rd day free) tickets you see on most other ticket websites.
USE DISCOUNT CODE "FAB7" FOR 7% DISCOUNT ON THE ADVERTISED PRICE, MAKING THESE TICKETS £39.77 EACH