As from January 1st 2012, the Pet Passport regulations have changed, making it easier to acquire a passport for your pet if you want to travel abroad with them.
Full details are on the DEFRA website at http://www.defra.gov.uk/wildlife-pets/pets/travel/.
If you're starting in the UK, all you need to do now is have your cat, dog or ferret microchipped and vaccinated against rabies, then wait for 3 weeks for the passport to be vaild for re-entry into the UK.
No more blood tests required!
The only problem that I see is that in the bad old days when your pet had to have the test to confirm that they had responded to the vaccine, about 5% of them failed the test first time around. Of the 40,000 new passports issued each year, that makes about 2,000 failures, who went on to have a second vaccine and then passed.
Now if we stop blood testing, the problem is that we won't know which 2,000 fail, and will be issuing them with passports anyway, even though they are not protected against rabies.
Just imagine how inconvenient it would be if you and your family all caught rabies during that lovely holiday...
My strong suggestion is that you have the blood test done anyway.