I can confirm that getting a sport pilot licence is pretty straightforward on the basis of another licence. I can recommend the Dülv who are very friendly and are like a club for promoting ultra light flying. You do need to take a test on pyrotechnics (simple) as all ultralights have a safety chute to benefit from higher max take off weight. Many aeroclubs have an ultralight section as it is much cheaper than ppl flying. The only real limitation is if you are a big chap you are a bit limited who you can take with you.