Jem in Europe- Miscellaneous.  The following countries had Jem in some capacity or another, but I haven't got enough information on them to have their own pages :)  The Netherlands especially seemed to have a large lot of Jem items!
 
The NETHERLANDS
The Show: It was aired in The Netherlands.  The music was kept in English, the rest was dubbed. It is suspected that Jem was on for one time only and probably not the entire series.  Thanks to Allanieew for that info.
I have also been told that the entire show was kept in English and subtitled into Dutch, and was possibly only aired up to the Glitter 'N Gold episode.  Thanks to Martijn Tulp for that info.
Hasbro & other licensed toys:
All of the first year dolls, and probably the rest of the first year line (including the Rockin' Roadster, Backstager and Starstage) was available there, in Dutch packaging.  Here's a picture of a Dutch 1st Edition Kimber (Thanks Laura (Badgerprincess))
From the second year, I've confirmed Rock N' Gold Jem & Rio (most or all of which seem to be the Caucasian version), Rock N' Flash Jem, Rock & Roll (Curl to us) Jem, Clash, Raya, Video and Danse dolls sold in Dutch packaging. Martijn Tulp says Jetta and Synergy were not available there. 
It is likely the fashions available there were from the 6 language series (this seems to be the norm for Europe).  Martijn Tulp says that the following were NOT available there: 1987 On Stage, Flip Side, Smashin', Rio and Music Is Magic fashions.
Stickers (sheet, blue background)
Puzzle- boxed, MB, 200 pcs. Featuring Jem in Award Night in front of the Rockin' Roadster (night scene)
The easiest way to tell a Dutch box is by the Dutch text, for example, Pizzazz's box says, "Pizzazz, Van De Misfits".  It only says "Truly Outrageous" on it, there is no Dutch equivalent used.  The dolls appear to be very much the same as those available in the US. Dutch and French text mean the box is probably Belgian.  For more information on Dutch box differences, see Jem 1st year boxes
Jem Comic Books; Just like the UK and Italy, the comic books were released in Holland with a new cover, translated into Dutch.  Thanks to Pete B. for this info!
BELGIUM
The information below in italics is from Nabil Khazzaka.  Thanks!
The Show: It has not been aired on Belgian television but it has been aired in Holland and in France.  Since Belgians can watch Dutch and French channels, they have been able to watch the Jem episodes.  French channel, TF1, aired all the episodes while the Dutch only aired the first series.  The reason why the Dutch did that is probably because Jem was not so popular neither in Flanders (Northern Dutch speaking part of Belgium) or in Holland.
I don't know if anybody told you already but in the French (dubbed) show Pizzazz' name was pronounced as "Pizza".  On the boxes however it remained "Pizzazz"
Hasbro's Toyline
Thanks to sven-ken of the Titi-chan forum, I am able to share scans of the 1986 Belgium catalogue!  Thanks also to Isabelle!  Oddly, though all of the 1986 line tems were featured in the Belgian retailer's catalogue, I haven't yet seen any Brussels/Hasbro MB S.A.-marked first year boxes, but instead:
"The dolls: "...the first year dolls were sold either in a unilingual French or Dutch box (probably depending on where in Belgium the dolls were sold: in Flanders or in Brussels/Wallonia).  It wouldn't surprise me if the Dutch boxes are the same as the one's from the Netherlands and the French boxes the same as the one's from France.  On the French boxes they talk about a special offer to get a poster with Jem star points which have to be send to an address in France.  The second year doll boxes have bilingual Dutch/French text.  Synergy and Jetta have definitely not been released.  And the second year Holograms and the second year Misfits haven't been released either (not 100% sure, though)" ... "I think "Flash 'n' Sizzle Jem/Jerrica" was called "Rock 'n' Flash Jem/Jerrica.
All playsets were available except for KJEM, Video Madness Playsets and the watches.  None of the second year fashions (Smashin' Fashions, Rio Fashions, On Stage Fashions ...) were available."
It is likely that the fashions available there were from the 6 language series.  
Other Jem Items:
I don't know of any yet, any information is welcome!  From Nabil Khazzaka: "As far as I know, in Belgian shops there has never been any merchandise like Board Games, vanity sets, comic books or sleeping bags."