The 1950 King George 6 stamp (KGVI) could have it's watermark sideways or inverted and be worth a few dollars.
The Machins (May chins) (guy who carved the bust Mr Machin.) are a tricky and deep subject. The lower values can be checked for one phospher tagging band vertically down the center or two bands down the sides OR no tagging at all which is worth quite a bit to those that collect such things.
Always the chance, best to check if you have a UV lamp (not sure long wave or short wave on the GB stamps check Robin Harris's Machin site: http://www.adminware.ca/machin.htm
for more details than you'd ever thought possible about a series of stamps.
You might be able to see the bands in normal daylight also as discolourations where the bands are.
I do not have a catalogue for the higher and newer values.
There can be differences in the paper, the printer, the prfs, the tagging, the actual colour and probably more things too. The socked on the nose (SOTN SON) cancel on the 2nd 10p is a wonderful cancel for what I can read of it. A closer scan would be appreciated by us who appreciate a nice cancel if you have the time. Oh, and post it in the Socked on the Nose thread here also.
The mauve coloured (I think) 65p Rose of England (War of the Roses etc) is a regional stamp and listed separately under the different regions (Scotland, Wales, England and Northern Ireland, all with their own regional symbols and colours. Some do collect these. I like the Welsh dragon stamp myself (not shown).
The higher values for the Machins may be worth more as they would be a not so many printed kind of stamp perhaps (hopefully)
How so ever they are all nice looking stamps as many would agree. Classic design, mostly great colours. Search on Stamp Community under Machin and there are a couple of good threads on them.