I never have 3 hours straight couse I have a 4 year old around me when I’m at home. Undisturbed 3 hours will happen on the exam only. But that’s OK, I’ve never done timed practice sessions.
7 to 8 years topic wise 2 to 3 times or until you can recall what is written in the sample answer sheets. For the first time solve like you are doing a BB or EOC i.e. not timed fully concentrate on keywords of the sample answers. If you can afford then buy IFT past exam solution videos (highly recommended) to understand how much to write. Although i have not used Mark Meldrums recent mocks developed by Bill; but i would have also used those if i were you for final practice.
You might consider going to a library or something then. The single hardest part of the Level 3 exam is time management in the AM section. That’s going to catch you by surprise in a fierce way on exam day if you don’t practice it.
I hear you Moosey! But, if there is someway you can manage to get a sitter or close family/friend to watch over for 3 hours, I’d highly encourage you to practice timed sessions BEFORE the exam.
Look I practiced like a madman ~10 (distinct) AM mocks timed before the real deal, and even I just barely finished everything on time, maybe with ~ 3-5 mins to spare. Time management is a major factor in passing L3.
I never done any papers more than once and only seriously against the clock 2-3 weeks before. Definitely would suggest practicing against the clock, in the actual AM exam I had 5 mins to review compared with the PM where I had a full hour!