^ lol ^
No seriously don't worry about them, a worried mind is not the best strategy for tackling any exam, so for a scientific calculator you can either buy one ~ there relatively cheap around £5.00 maybe, your School may even sale them ???, failing that speak to your maths teacher or another teacher asking if you could borrow one to use in the exam.
I totally know where you are coming from it was only a short time ago i was sitting my GCSEs and i was just the same - nervous, but a calm, positive attitude (easier said then done i know) can help maintain a clear mind plus loads of revision spaced over a set period can ease the tension, as for non-revision techniques try a site like BBC Bitesize may be they can advise you on how to tackle those specific types of question.
To be honest i failed miserably on my mocks, it certainly kicked me into touch and i used that experience to prepare myself better for my proper GCES exams, so its not the end of the world if you don't do too good as it highlights not only what areas you need to focus on in regards to revision but also your exam preparation techniques.
All now i can really say is good luck