You can apply to Economics at Cambridge and MORSE at Warwick if you would like. Warwick is aware that their course is quite niche so they know that people will be applying to different courses elsewhere so your personal statement can be mainly Economics; if your predicted grades fulfill the standard or contextual requirements it's unlikely you'll get rejected (historically, the course has a 95% offer rate).
Also, here is some info to keep in mind about MORSE. It is led by the Statistics department, it's more of a stats degree than an Economics degree. It is highly flexible and gives a broad basis on knowledge in your 1st year then in later years, you go down the stream of your choice, you specialise in what you like the most. It's also a great degree if you are considering becoming an actuary, as you can gain actuarial exemptions (with the relevant modules).
If you are considering Cambridge too, check out the course modules for Economics that may give you a sense of how mathematical it is. Also, Cambridge only requires FM for certain colleges but it is highly recommended regardless of college. Good Luck!