You seem to have nailed most of them.
Pic 15: Juv Siskin: finch bill,rather broader wing bars than a Serin(serins are probably rare that far north).Streaked flanks,yellow tone to upperparts,yellowish sides of outer tail feathers.
Pic 16: Typical Fieldfare.
Pic 17,18 & 20 are all Northern Wheatears.Very variable in appearance -18 is a male and may be the Greenland race but never really easy to differentiate in the field. They are best identified on hand measurement - Greenland birds being significantly bigger (upto 25%) than the typical 'European' race.
19: is tough.I'm going for a Chiffchaff but can't be absolutely sure it's even a Phyllos! Dark legs, overall brownish hue to upperparts. Looks suprisingly chunky but could be the angle. Usually identified by frequent 'tail dipping' behaviour.Another photo might help!
The last couple of thrushes are again young blackbirds.
E