Hi mate its possible to do if you put the effort in it isnt easy but possible as i had no experience of three phase inspection and testing before hand but i studied every day for 4 month its no walk in the park you have been given some good advice on revision
the books that have been suggested will help a lot focus mainly on the
GN3 as about 80% of exam based on this
then
Electricity at work regs 1989
GS38
another good book is Cristopher kitchers guide to inspection and testing its only about £11 and worth every penny explains it in a easier manner than the other books i have read
this the link to the book on amazon
Practical Guide to Inspection, Testing and Certification of Electrical Installations: Conforms to 17th Edition IEE Wiring Regulations BS 7671:2008 and Part P of Building Regulations: Amazon.co.uk: Christopher Kitcher: Books
practice loads of past papers as some of the questions crop up again and again plus it will give you a feel of how the C&G want it answered
they especially dont like incorrect terminology
learn all about the different test procedures and how to explain in bullet points
can be done with drawings as shown in gn3 or without also sometimes your asked for calculations as part of the answer
practice calculations for resistance and volt drop
the exam success is a good help keep practising with it until you can get a higher mark as possible without looking at the answers it will also give you a feel of the time taken for each question
Earth fault loop diagrams for all systems , TT, TN-C-S, TN-S, IT fully labelled with correct terminology
your course will show you a lot of this so practice in between the weekly lessons so its second nature
practice inspecting and testing as you have been advised on your system using safe isolation
there are loads of threads on the forum covering the 2391
a good one is the section 301 thread which is a sticky in the general section by Amberleaf his time and effort in posting this info i found a great help as there are sample questions etc in there
dont be afraid of asking mate thats what the forum is for
Good luck to you