People always say this, but the fact is I have a £20 note in my wallet and I didn't make it myself.
If the will is there, it could be done.
P.S. Most of the countries these people travel through have I.D. cards, so why not stay there and get a fake one? Because it is easier to come to the UK where there are no I.D. cards at all.
It isn't just about I.D. cards though, its I.D. cards linked to employment. How many car wash places near me, how many take-aways near me would be shut down if the employees were unable to show identification to prove they were here legally?
I actually suspect the current government likes it the way it is, ok someone may be in the non-tax (PAYE) economy working in these places, but they then spend their earnings in other places which does garner VAT and adds to the wealth of the country. That is why they talk tough, but don't ever do anything.