Thanks everyone . I have struck out the Weekly boarding schools from my list. Initially I applied for Westminster and Tonbridge - but we did not go for their test as I understood the implications of weekly boards bit too late :( It sounds very silly to me now, but at the time of applying, I was completely in dark about these terms.
Thanks for Charterhouse , Whitgift and Harrow pointers. It's already overwhelming to take these assessments. I will be more focussed on full boardings.
Regarding DS's ability , he is definitely not a genius, but has always been in top 2-3 in his class at previous prep school. He is doing very well at MGS. There are a few genius in every subject who score full marks in anything and everything, but he is not behind them. If I felt its beyond DS's calibre, I would not have wasted my time.
However I agree to some extent that the competition level of Manchester can't be compared to these World schools . Winchester will be hard to crack, so I am leaving everything to his natural ability. DS is sensible , sincere, intense type. He takes everything very seriously and is very clear about his shortcomings . He plays only one sport - Cricket, but he plays it well . So I will leave it to DS. And yes, he may not get a place again, we are prepared for this. But from what I have heard, I think he stands a fair chance. I also think he was given a fair chance at Eton.
Realistically speaking, I have only 3 full boarding schools - Winchester, Wellington and Kings Canterbury.
I will look up at some schools suggested and extend my list. Proximity to airport will be my major concern.
All criticism is welcome !! Remember its not just me who is getting suggestions,- some hapless and clueless mother in year 2020 may find all this discussion very enlightening .