I agree. Immigrants don't make a dent on overpopulation. With or without immigrants arriving in the UK, there is still one born every minute. Still first time buyers looking for a home. Immigrants account for about 11% of our population here in the UK (Higher than 10 years ago admittedly), but our population has been increasing for the past 10 years from 53 million (2001) to 63 million (2012). Immigrants aren't massively responsible for that as they account for about 3 million. Our population is just naturally increasing, we can't do anything about that.
Additionally, Romanian and Bulgarian immigrants won't be bringing any diseases that don't exist or can't be suppressed. Malaria? Bulgaria is Eastern Europe not Africa, there won't be an influx in that, that will be due to climate change as it is too cold for malaria to survive here. Other diseases can be cured or slowly treated (HIV, TB). These Eastern European countries don't have any more exotic diseases than we do. Besides, they won't be able to come to a country if they are riddled with diseases.