purely going on your opening post, and reading no doubt poorly between the lines the main (sole?) requirement is for a trainer is for motivation, rather than individual planning etc.
In which case, blinkybaz pretty much has it ... you don;t need to pay someone £50 and upwards a month or whatever... you just need to find a "Jiminy Cricket" that works for you.
And - WADR - coughing cash to a coach won;t really make you train - what are they going to do if you still don;t get out and do it? Tell you off ? - oooooo!

Tell you NOT to waste your £50 a month after all (possibly the best advice you'll get from them

? If the financial outlay is the motivation 9ie I am paying for it so I had better do it), then why not pledge £50 a month to a charity close to your beliefs etc, and tell your self the kids/animals/amoeba/one parent bus shelters will SUFFER if you don;t fulfill your schedule properly which means you WON@T pay this month's £50.
Just an idea

didds