Erm, I haven't looked at the calculations because there were too many unknown variables before. Although I see you've just posted the full time hours are 35 per week so that helps.
Not very helpfully the government is currently reviewing guidance for calculating term time only workers holiday 
To give a reasonable estimate I would need to know how many weeks you employed for per year and how many of those are work (the balance being annual leave). At the moment I just know you work for 40 weeks per year. Are the 30 days full time staff get inclusive of bank holidays?
If I assume full time staff get 30 days in total I calculate it like this (although it is very late so I'll need to check this with fresh eyes and brain tomorrow):
FTE get 6 weeks holiday per year. So I calculated the percentage of time off on annual leave as 13.04%. The 13.04 per cent figure is 6 weeks' holiday, divided by 46 weeks (being 52 weeks - 6 weeks). The 6 weeks are excluded from the calculation as the worker is not at work during those 6 weeks.
Then I calculated 113.04% of 40 weeks which is 45.216 weeks. I would expect this to be your actual contracted annual weeks.
Then because you only work 28 hours and FTE is 35 I worked out how much you would get if you worked a full year ie 52 weeks (22,000/35) x 28 = £17,600.
Then to work out the actual annual salary I take £17,600, find the weekly rate and multiply it by the number of contracted weeks (17600/52) x 45.216 = £15,303.88 (rounded up to whole pence).
So I get £15,303.88 which would presumably be paid in 12 equal instalments which is £1275.32 gross per month.
So very similar to your dh! I used the holiday calculation for casual workers from Business Link and gave you my workings out so you can compare.