He's using Cockney rhymning.

"Hey now, Lenny is my China so you better not donald duck with him or I'll get barry with you and kick your april." translates as:

"Hey now, Lenny is my MATE so you better not FUCK with him or I'll get ROUGH with you and kick your ARSE."

China plate = Mate
Donald Duck = Fuck
Barry Cluff = Rough
April in Paris = Aris = Arse

And "I had a butcher's at your boat race and it's Cambridge and Oxford. Definitely not Calvin Klein. Did someone take a camel's on it?" translates as:

"I had a LOOK at your FACE and it's AN UGLY FACE. Definitely not FINE. Did someone take a SHIT on it?"

Butcher's Hook = Look
Boat Race = Face
Cambridge and Oxford = Ugly Face (don't ask why it doesn't rhyme)
Clavin Klein = Fine
Camel's Hump = Dump = Shit

Sor'ed in'nit?