"London is calling," Cramer told viewers as he used the pomp and circumstance of the royal wedding to introduce a diversified portfolio of British stocks to help round out some American investments. Cramer said Britain is one of the most investable countries on earth and investors need to give these names a second look. First up was mining giant Rio Tinto ( RIO). Cramer said with China's slowdown almost complete, Rio will see rising demand. The company is aggressively paying down debt and has a $5 billion stock buyback program. Next on the list were British American Tobacco ( BTI) and National Grid ( NGG). Cramer said British American has 22% cigarette market share worldwide and has a 4.3% dividend yield, while National Grid is a solid performer with a 5.6% dividend yield. Also on the list, publishing house Pearson ( PSO), a company Cramer called one of the best in the publishing business. He said Pearson is an amazing story and has a 3.3% dividend to boot. Finally, Cramer gave the nod to Vodaphone ( VOD), in part for its 45% stake in Verizon's ( VZ) wireless operations, but also for its 360 million other customers in 30 countries around the globe. Cramer also outlined a group of British stocks investors should avoid. He said while the British economy may be on the road to recovery, not all of their stocks are participating. The first stock to avoid was BP ( BP). Cramer said BP is still too controversial and won't return to pre-spill production levels until 2016. The company also has a dicey Russian partnership deal and poses far too much headline risk. Also on the no-no list, Lloyds Banking ( LYG), a British bank Cramer said is two years behind others in its recovery. Cramer said he'd also avoid British Telecom ( BT), a struggling landline telco that lacks a big dividend yield like its U.S. counterparts. Finally, Cramer said he wouldn't recommend liquor giant Diageo ( DEO), as the weak dollar continues to hurt this company's American profits.