How does getting a low grade (47) on 15 credit module affect my degree classification

It's clearly going to affect your final grade more than failing a first, or even second year module would, but I'd suggest it's not entirely calamitous. Without knowing in details your course regulations, it's difficult to say the exact impact it's going to have How many final year modules do you have? Also, some courses will take your best results in a defined number of final year modules, whereas others will take an average mark...lots of variables.

I have three core modules worth 30 credits each and two option modules worth 15 credits each for the the final year and the same for last year.

I remember my lecturer saying that they take the best 90 credits from the final year and then the rest from the second year but on the regulations file I checked online, it talks about how altogether the credits are 240 and surely that means all 120 credits from the last year and all 120 credits from the second year are counted? If that's the case, how does this affect my grade if it's going to be counted.

I've got a meeting with my lecturer set up but that isn't until 2 weeks later and the worry is eating at my mind atm.

Each University will have their own ways of working out their classifications so it's hard to judge precisely the impact a mark of 47 will have, however I don't think there is too much to worry about if you're managing to achieve 2:1's and above in your other modules.

I'm sort of in the same situation as you, as I managed to royally screw up my second year results where I got 40 in a 10 credit module, and 41 in a 20 credit module, yet somehow there is still a strong possibility that I can achieve a first overall.

So I would advise to check on your course website and try to have a good look around to find the information regarding to how your course determines your classification. It may be a simple method such as working out the weighted mean grade, or they may even utilize a couple of different methods (which is what my course does).

I was very anxious starting my 3rd year after having a mixed bag of results last year, however after checking to see how my classification was determined I soon calmed down and was able to look towards the positives and see quite clearly what would be required of me this year.

I understand your worry - and it doesn't help when there is contradictory information. I can't comment on which of these is correct, as it really does vary between universities - however the best 90 credits from the final year and the rest (being 30) from the second year sounds the more credible option - 240 credits is two year's worth, but I don't know of a university which would use all 240 to calculate the final grade. Basically, I don't actually think this is going to make any material difference to your final grade, so long as you don't get another one, and the rest of your modules are on target. So don't worry unduly about it. Courses are designed so a single muck-up doesn't adversely affect the final grade - think about it: it would be grossly unfair to strike down a final classification just because of a piddly little 15-point module!

Thanks very much, you've eased my mind. As for the 240 credits, this is what it says and I don't understand:
"the classification of the award shall be calculated on the basis of the best 240 credits at Levels 5 and 6, at least 90 credits of which are at Level 6. A classification average over these 240 credits shall be calculated. The average of the marks for the best 90 credits at Level 6 shall contribute two thirds of the classification average; the average of the marks for the next best 150 credits at Level 5 or Level 6 shall contribute one third of the classification average."

When they say the best 240 credits, how does that make sense when there are only 240 credits in total? Does that mean that all the credits will counted?

If you tell us the course/university and your other marks then we'll probably be able to help.

If not then someone in your course/school/faculty office or student records/registry should be able to talk you through this now rather than waiting a fortnight.

The statement you've copied means that your best 90 credits count for 2/3 and your worst 30 credits from Yr 3 and all of Yr 2 count for 1/3