How would a microlight compare to this
The biggest single fixed cost is insurance after hangerage, so if you can take that out of the equation you are looking at cheap flying. I imagine microlights are similar to Permit aircraft, i.e. £300 to £400 a year for permit renewal, and say £100 (err on side of caution) for 25 hour oil change, etc. Insurance is the one you need to get a couple of quotes on; much of the premium is dictated by hull value.