You may well have had the email or seen the adverts, but in case you didn't, Ancestry UK are allowing free access to their immigration records for eight days - 29th August to 5th September. This means that you will get the benefit of Worldwide Membership for that time. Check out Ancestry for yourself - I've even managed to put in a posh search box!
Can I also recommend Ancestry's occupation records. The recently released Railworker Records have proved a treasure trove for me, providing one great-great grandfather's date of birth, date of retirement, and his promotion records. His son didn't fair so well - he was sacked for absence without permission, which I notice ties in with the date of his son's birth - clearly he decided to take paternity leave before it was even invented. Also found a nice record of a payment to a great-uncle for his help in fire watching during World War Two.