I don't believe there's a single bit of evidence that immigrants have "decimated public services," as you put it. On the contrary, there are a number of factors that strongly suggest immigrants have propped up public services:
- Most immigrants are of working age
- The biggest consumers of public spending are the young and the old (through education, healthcare, and pensions respectively)
- The typical newcomer has to wait 5 years before they can claim any public funds (it's called "no recourse to public funds"), so they, by definition, cannot "decimate" anything
- Newcomers also have to pay the NHS surcharge for the duration of their visa. So, not only are they typically of working age, so less likely to "need" the NHS, the taxes they pay are topped up by a dedicated payment for the NHS (that they often won't use).
- The demographic situation in the UK is a mess, with pensions taking up an ever greater slice of public spending. This pension is paid for out of working people's taxation, but the proportion of workers to retirees is significantly worse than it was when the pension was introduced (and people obviously live much longer in retirement than they did back then). So we need more workers to pay for it. The birth rate isn't high enough to do that (and even if it did increase, it would take a long time to make any impact). So, again, those immigrants you hate, are actually paying for pensioners' retirement.
Now, there are things that the government should do. The first is to stop using foreigners as an easy "out group" they can heap all the blame on. This is cheap, especially as those people have no democratic input, even if they've lived and contributed for a generation. Secondly, the government can get much better at supporting local communities if populations change. This should be irrespective of whether the change is because of immigration from abroad or population movement from within the UK. The passport is irrelevant, and this should apply equally to those communities that are growing as to those that are shrinking (those "left behind" places).
Sadly, they don't tend to do this, as it's much better to do #1 and blame it all on foreigners who can't vote them out. It's perhaps saddest of all that people like yourself swallow their lies wholesale and let them off the hook.