Hi. I took HSK 5 last year. I didn't attend any HSK intensive course, though I did lots of mock papers.
Sorry if you have already known this, in case you don't know, it may help:
http://www.chinesetest.cn/godownload.do
Besides, I bought some materials which include not only answers but also explanations.
You may try this bookshop:
Union Book Co Pte Ltd
Blk 231 Bain Street, #03-01/59, Bras Basah Complex (S)180231
Tel: 63367237
Opening Hours: 10:30-6:30 (better check before you go, it might changed)
When I took Level 5 exam last year, I felt that the listening part are much faster than the past exam collections which I downloaded from the Official website.
Sorry if this is not the info you are looking for, but I think if you are already at this level, it may not necessary to take a course.