You need an EASA STC. I got mine from
this company in Switzerland for about 500 Euros two years ago. Depending on the aircraft, the STC only consists of a sticker next to the fuel tank or the replacement of hoses and pumps. According to Peter's
website (not the TB20 Peter), there is only one company in Holland that sells the EASA STC today.
Overall it's great but there is a big issue: ethanol. The STC limits ethanol content to 1% and you often find that 91/96 UL fuel contains more than that. The UL engines (Rotax) can take up to 5% and you never know what the ethanol percentage will be. At our aerodrome, it ranges from 0.1% to 2%. When it's above 1%, I mix with avgas to keep it below 1% (more or less). For this to work it is important that your airfield always accurately determine the ethanol content after each delivery and clearly indicate it.