Registered dietitian salary in the UK. The average salary for starting registered dietitians in the UK, based on Prospects, is Â£21,176 to Â£27,625 per year. Dietitians who are at a specialist level earn Â£25,528 to Â£34,189, while those who are at an advanced level make around Â£30,460 to Â£34,189.egistered dietitian salary in the UK. The average salary for starting registered dietitians in the UK, based on Prospects, is Â£21,176 to Â£27,625 per year. Dietitians who are at a specialist level earn Â£25,528 to Â£34,189, while those who are at an advanced level make around Â£30,460 to Â£34,189.