Don't think RYR have had any B737-500s but i'm happy to be corrected.
I remember seeing their BAC1-11s in BHX a few years ago, since then they've had B737-200s from various sources (Lufthansa, Transavia & Britannia to name a few), then the B737-800s which they ordered from Boeing. After the buyout of Buzz, they had the BAe146 & B737-300 in the fleet (both types now retired).
I also understand they leased 2 B737-800 from Excel for a short period
WNC