Ok so excluding the ponies it works as below and if I have confused things further I apologise
Plates
EURO: x 4 darker blue than US
UK: x 6 darker blue than US
US: x 6
Cups
EURO: x 4 darker yellow than US
UK: x 6 darker yellow than US
US: x 6
Big Plate
EURO: x 1 darker blue than US
UK: x 1 darker blue than US
US: x 1
Cake Pieces
EURO: x 6 with yellow decoration
UK: x 6 with yellow decoration
US: x 6 with gold decoration
Banner:
EURO: x 0
UK: x 1 dark turquoise trim
US: x 1 blue trim
Candles
EURO: x 6
UK x 6
US x 6
Ribbon
EURO: x 1 yellow
UK: x 1 light yellow
US: x 5 [green, orange, pink, yellow and silver metallic]
Invites
EURO: x 3 with Tutti Fruitti
UK x 5 with Tutti Fruitti
US x 5 with Morning Glory
Hats
EURO: x 4 [yellow & blue diamonds, green & pink waves, blue & orange balloons, yellow & red circles]
UK: x 4 [green & pink waves, blue & purple stars, yellow & pink fish, yellow & red circles]
US: x 5 [yellow & blue diamonds, green & pink waves, blue & orange balloons, blue & purple stars, yellow & pink fish]
Balloon
EURO: x 0
UK: x 1
US: x 1
Party Favours
EURO: x 4 [blue, orange, green and pink]
UK: x 5 [blue, orange, green, pink, purple & yellow]**
US: x 6 [blue, orange, green, pink, purple & orange]
There are some colour differences between the versions on each side of the Atlantic
**This set is notorious for coming with 5 favours in a variety of colours sometimes even 2 of the same colour
Pin the tail
EURO: x 1 Tutti Fruitti
UK: x 1 Tutti Fruitti
US: x 1 Party Time
Straight tail
EURO: x 1
UK: x 1
US x 1
Curly tail
EURO: x 1
UK: x 1
US: x 1
Blind folds
EURO: x 2 [1 x orange and 1 x purple]
UK: x 0
US: x 2 [1 x orange and 1 x purple]
Brush
EURO: x 1 bright yellow bird
UK: x 0
US: x 1 purple/pink star brush
Comb:
EURO: x 1 bright pink crescent moon
UK: x 0
US: x 1 sun comb
Sticker:
EURO: x 0
UK: x 1 Tutti Fruitti puffy
US: x 1 Best Wishes flat
The US set also includes a present box, a poster, a birthday card and a box with "party pants"