Sebastian
Early fall in the Carribean and Latitude 22 is hurricane season.Once into October a much safer bet but still can be windy and best DIY opportunities are a good 3/4hr drive from Cancun.IT is fun but lumpy and better in a Jeep.
Pacific Mexico is a good bet especially Zihuatanejo for Jack Crevalle,Roosterfish,Sailfish,Tunas,Dorado/Mahi-Mahi but £50 per day boat is not reality.$250US for a panga + tip.You can do deals dockside but you take your chances.The top panga Captains are worth every cent.If you need any more info on Zeewat let me know.
Baja Mexico has miles of unspoilt beaches and coves.Accommodation around Los Barriles is very reasonable.Fishing can be wild/incredible.Go on the last quarter or dark side of the moon.They have Kayaks for hire in some spots here.I would live there if I could....

Flight gateways from Europe via Dallas and Houston.From UK we could make a same day connection via Dallas and be in Baja around 7pm.Good luck.
JP