In terms of drivers. You are not entitled to a blood test. The Road traffic act allows Police to require a breath sample, and doesn't place any obligation on Police to offer, nor option by the arrested person to to demand, a blood or urine test
The evidence of an evidential breath testing machine is suffiecent, if the sample you give is over the prescribed limit.
If you give a sample over the limit, but close to it, you will be given the option of a blood test. Everyone of those I've seen has given a result more than the breath tes reading, except one, where it took the doctor over an hour to arrive, and that one was only just less than the Breath reading when analysed.
However, those results are all from Road Traffic Act requirements, and in general those are taken not long after the arrested person has stopped drinking.
As for the aviation side of it, the legislation says the test can be blood, urine or breath, and it is the Police's decision. However, there is an agreement with the CAA that blood will be used. That is an agreement, not law though.
On the plus side, it means that time between screening test, and blood test being taken can be up to an hour and half, ( an evidential breath test would be taken in less than 30 mins) in that time the BAC will continue to drop (assuming that the arrested person hasn't just stopped drinking). So an 'avarage' person will loose about 1 unit, or twice the limit imposed by the act, before the blood sample gets taken. That weeds out those who are just over the limit at time of screening.
There are a lot of old wives tales about breath tests, one of them being about the levels of BAC that can be detected by breath machines, it is from zero upwards, and can easily identify the limits imposed by this act. I would be treat those tales with a great deal of caution, most if not all, are rubbish, and most have been tried as a defence, and been dismissed as not having any validity, after evidence of expert witnesses.
As for the sentence in this case, it seems very harsh, I agree, especially in comparison to the US pilot. But then in neither case was all the mitigation reported, so it's difficult to see why there's vast difference.