Polar,
I did my IR sort of part time. I started in the sim every Saturday for about a month and then finished off with two weeks intensive flying. The two weeks of flying was very hard work with very long days, but it can be done if you go for it.
I went to PAT at Bournemouth.
Computer IR sims; get a freebie at
http://www.visi.com/~mim/nav/
I used it for all my practice, especially the holds.
Good Luck,
Vigi