Amanda, the 'breastfed from birth' charts are indeed different from the WHO charts. Personally, I think the breastfed from birth charts are based on poor data - you can check this if you like, and you will see that the sample used is tiny compared with the stahdard charts which are based on several (eight, I think) data sets not of bottle fed babies but of a mix of babies, some of whom will have been breastfed and some of whom will have been mixed fed, and some of whom will have had only formula, some of whom will have had early solids.
They are longitudinal charts, which is a robust way of tracking the growth span of a population, and which is a proven useful way of spotting babies at risk of failure to thrive/faltering growth, especially when used in conjunction with thrive lines.
Charts are used very inappropriately in the UK, by health professionals who are not well-trained in interpreting them (many clinics do not use the thrive lines, for example). They cause huge anxiety in HPs and in mothers. The training in breastfeeding HPs get is also poor - put poor chart training with poor bf training, and you have a disaster for breastfeeding.
Of course there are babies who are not nourished well enough at the breast, and the charts can sometimes alert HPs and mothers to this possibility. When this is the case, there are ways of supporting the breastfeeding and ensuring the baby gets what he needs at the breast - when this is not done, at best babies risk weaning/moving to formula unnecessarily, and at worst, you get poor mothers like trefusis (brave story, trefusis) driven into severe anxiety.
It would be important for your PCT, Amanda, to support your training in the use of the charts and to decide which ones are the most useful. There are many experts who feel the 'breastfed from birth' charts are just not good enough (Royal College of Child Health, for one, has refused to back them).