Firstly, my apologies if this has been covered before - is there a way to search 106 pages of freeview topics easily?

I live in Whitby, and have marginal reception of freeview from Baxter's knob. Freeview say my reception is "likely with a high antenna".

I have tried a 43 element UHF antenna, and currently have a phased array antenna, mounted at the highest point of the roof, on a 1.5 metre mast. I am not line of sight with the mast, and google earth tells me I have 33 metres of hill between me and the mast! On the skyline between me and Baxter's knob there are trees! I have a mast top amplifier between the antenna and the freeview box.

When the weather is good, I get near perfect reception on channel 57 (Kordia - Prime etc) - just the occasional breakdown of sound or picture. I sometimes get quite reasonable reception of the other two channels (51 and 53). My freeview box (Dishtv) shows between 75% and 95% strength, and quality between 65%  and 95%. However, in 51 and 53 they occasionally disappear altogether.

If the weather is bad (high winds or heavy rain) reception is almost non existent on 51 and 53, and irritatingly patchy on 57.

Firstly, why is Kordia so much better than the other signals?
Secondly, am I likely to get better reception with a better antenna or a professionally installed antenna? What would be a better antenna in these circumstances.

Freeview have told me that they are not adding any more transmitters, so there is little hope of getting it relayed through through the Whitby repeater or similar, and Kaukau, Haywards and Fitzherbery are all worse propositions then Baxter's knob, being even further from line of sight, and much further away.