Is Immigration Good or Bad for the UK?

With the opening of the EU to Bulgarian and Romanians there is a great deal of talk over immigration and the argument always seems to fall on the question of "Is immigration good or bad for the UK?" 

Personally my answer to this would be Yes, of course immigration is both good and bad for the UK, after all just about everything that happens will have a positive and negative effect depending on who you are and what you are looking at. Immigration brings many wonderful things with it it terms of diversity and bringing in hard working people that are able to contribute to our society. However there is also potential for it to have negative effects especially for people who are out of work and now have a wider pool of competition and there will obviously be strains on a local economy if we have a situation where there are not enough houses being built for the demand, it is obvious increasing demand would have a negative effect if supply is not also increased.

I do think it is quite funny however when I read articles like this one from Left foot forward and they make the claim that immigration is not a bad thing as

2) Migrants from Eastern Europe are less likely to claim benefits than indigenous Britons
*Not a direct quote as I spell checked it first

Now this "fact" doesn't surprise me at all as I have never believed that people will travel halfway across the world just to live on benefits as after all being an Immigrant takes guts and determination and these are not the qualities of people who want a life on benefits, I think it is much more likely that the migrants who are on benefits came here looking for a better life but instead were sucked into our welfare poverty trap.

My issue with the fact is that if they are saying migrants are less likely to claim benefits than indigenous Britons then are they saying that those indigenous Britons are claiming benefits instead of working, as a life choice? Surely if we are to look at the fact that migrants are in work and not claiming benefits as a success then we should surely recognize that the swing side of this is that indigenous Brits are choosing not to work.
After all if British people are being forced onto benefits due to immigration then this benefit bill needs to be offset against the tax revenues paid by migrants (If the unemployed British were working then the tax revenues would be the same.)

To be honest this backs up what I have found from my own experience so I am not surprised however I have often read from Left Wing commentators that nobody wants to be on benefits but there aren't enough jobs to go round - surely this would therefore create a direct negative to having migration.

Unfortunately I think the truth is that many people who hold both of these incompatible opinions is that:

Migration is good as migrants tend to vote for left wing parties and unemployment is good as the unemployed tend to vote for left wing parties.

For my two-pence worth, I think migration is a great thing and should be encouraged and the answer to the concerns of overcrowding is that we should be getting out there ourselves and understanding a bit of the world outside our own borders.