People are not against immigration per se.
But on a daily basis we see a situation where we have 2.4 million people on the dole (or whatever the figure is). so we are paying all these people NOT to work.
And at the same time we are allowing (or not stopping) thousands of immigrants coming in who DO find jobs and WILL work.
So I think the anger for many people is that politicians for decades have seemed "happy" to pay out benefits to people who have no intention of working AND had a very lax border controls to allow people in who do seem to be able to find jobs.
Other countries, like say Australia or the USA, are very strict about who they let in. You have to have a job promised to you, or skills the country needs.
We seem to let in any old rubbish, people with no skills, who cant speak English, and have no intention of integrating. We seem to have no control sat all.
We also seem to allow them to bring in their parents, many of whom are of course very old and are just going to be a burden on our society (as if we have not already got a problem with an aging population the last thing we need is more).
I think MUCH of the anger with immigration is how poorly our politicians have handled the whole thing, not just Labour, not just the Tories, but all of them, for the last 40 or 50 years.
THAT is where much of the anger is, against the politicians.