If you have 2 pints of shandy half beer half lemonade will this have the same effect on you as 1 pint of beer or will the effects be less as the beer in the shandy is diluted?

The alcohol content will be the same. However, chances are you will drink the two shandy's more slowly then one beer. That means your body will burn off more of the alcohol before you are finished, so your blood alcohol content will be slightly lower.