Broadly, in the last century, those who immigrated to the UK were either from societies with cultural traits broadly in line with the UK (whether that was as a result of British colonisation or not), were highly-educated, or were hard working, although I'm aware that in certain areas this was not always the case. Over the course of this century so far, the balance has shifted slightly to encompass those with no cultural similarities at all with the UK (including those with values, or attitudes - whatever you want to call it - totally at odds with those of native Brits and many established immigrant communities), poorly-educated, clannish, and sometimes actively quite hostile to the UK and its people.
Posters can often (not unreasonably) claim that it's wrong for British pensioners to tip up in Magaluf and sit at Ye Olde Irish Pub and yell 'un beerio por favor Manuel' all day, but can't seem to apply the same thinking to the fact that we're now seeing an influx (and yes, not all recent immigrants, by any means) of those countries' equivalents of the scallies and yobs you'd happily move away from on a train if they were white British.