Hi,
I am looking into some ops service providers for my near future operation and prices go from a few pounds to stupid amounts of money.
Basically what I have decided is that its not worth getting only a flight plan service as you can get much more for a small amount of money.
I have found very good prices for ops service for prices around 50-60 pounds per flight but most providers offer a "fixed" price per month. If you fly a lot it can be interesting.
When I finally have all the info I will share with all of you my findings if the moderators don't mind.
Don't pay more than 65 pounds per flight for a normal support is my conclusion.