Don't know about service intervals (I just slapped new oil in every 2,500 and filter every 5,000. Regularly check chain for slackness/lubage, check oil/brake fluid/coolant levels, check tyres and brake lights)
As for the restrictor kit, a lot of mechanics do them but it will need to be ordered in. Expect to pay £150 for the kit and about £25 for fitting. It's probably not even worth it though