Total time for me to complete the Night Qualification was 4 hrs 55 mins dual, and 1 hr P1 to complete the 5 TOs and LDGs.
This equated to a cost (at £94 per hour solo and £125 dual on a C152) of £709. I seem to remember it cost around £80 to have the qualification endorsed on my licence, so all in all, it cost me around £800 in total.
Although I assume your figure is based on 5 hrs total, i.e. completing in minimum time. Had I done the lot in 5 hrs, the total cost would have been around £700.
There are no landing/T+G fees for based aircraft where I was flying from.
My initial reaction to your calculations is - that's expensive! Although Biggin Hill (and in fact all the London aeroclubs) is bound to be more costly - my training was undertaken at a smaller, close knit community type of airfield in rural East Anglia!
I hope this helps - it may be well worth looking around and accepting a longer drive to the airfield.
All the best.
