Great question! I think there is a huge difference between gym fit and riding fit. I think for riders it's important to develop long & lean muscles vs short weight training type muscles. (I might be wrong....) The thing that comes to mind with that for me is my hubby, he has massive heavily toned calf muscles. When he gets on any of my horses they tend to move off his leg without him realizing he is giving them leg simply due to the size of his calves. He doesn't ride often but has spent enough time on one mare that she now is tougher for me to ride and I have to be overly leggy with her constantly because of the difference in our leg size.
For me finding time to truly workout is tough. Between being a mom and toting a kid to all of her sports & activities (at 5 she already plays soccer, softball & does competitive gymnastics) on top of running the farm by myself, my hubby works a lot so I do the lion's share of the physical labor involved with the farm. I clean all of the stalls, do all of the feeding and daily stuff and I also help when it's time to bale hay.
My background - I am the last rider in my family (besides my daughter, but at her age she isn't a major influence in the work part of things HAHAHA) I own 10 quarter horses, 3 being breeding stallions. I keep all of my own fit as well as taking 2-3 training horses at a time & I have 11 riding students that come on a weekly basis for lessons. I myself ride working ranch type horses, reining, cutting, working cow horse but do ride hunt seat on occasion to keep myself refreshed and use different muscles.
I make time at night to put an hour in on the elliptical trainer and I do yoga in the am before I head out to the barn for the day. I try to get to Curves for circuit training 3 days a week. I don't do any strength training other than the resistance training at curves - I don't know if you have them in the UK? All of their machines work on hydraulic resistance instead of free weight. This seems to work for me as it's hard to find time for more than that. Do you think this is a good exercise plan for a 30 something soccer mom/horse trainer?
Life is like a camera. Focus on what's important, Capture the good times, Develop from the negatives and if things don't work out, Take another shot.