dieticians/weightloss

First, I'm going to point out that weight loss is simple in theory. Simple as in the principles are not complicated, not as in it's necessarily easy. All you have to do is figure out how many calories you're consuming per day, assuming you're at a fairly stable weight, and eat less than this over a sustained period of time. There are any amount of sites and apps out there that will give you the energy and nutritional content of your food.

Secondly, I'm aware that, even given the information above, some people find it incredibly difficult going it alone and that the structure provided by professional help could be needed to get you on your way to achieving your goals. It's hard to put a price on health and happiness in self image.

Thirdly - and I'm sorry to say this - I seriously doubt that any established dietitian is going to offer their services for anywhere near as low as a tenner per week. This is just an educated guess and I'm open to correction here.

EDIT: Quick addendum. You seem to be using the terms "dietitian" and nutritionist" interchangeably. They are not the same. Dietitian is a protected term, like doctor, that requires a minimum of a BSc. in the appropriate course. Nutritionist is not (this is certainly the case in the UK, and I think it's the same in Ireland. That's not so say that there aren't competent nutritionists out there, but the fact is that I could legally set up as a nutritionist tomorrow despite having nothing but the most rudimentary knowledge in the field. So if you do go down this route, make sure the service you're enlisting is reputable.