how to check marriage certificate of someone living in scotland married to a woman in china january2013?

I am afraid that it's not an easy job. If he officially married a Chinese in PRC, he should have registered at the local civil affairs bureau and get Chinese marriage certificate. If you really wants to figure it out, you might ask the local civil affairs bureau for help. Or contact the girl he married for confirmation.

will it be registerd in united kingdom as well

No, this is not mandatory. But, he should provide a single certificate in UK in order to get marriage registered in China, and this certificate should be authenticated by Chinese embassy/consulate. Maybe you can have a try to contact the embassy/consulate for this.