If the hospital said you should have a half unit pen, you need the cartridges for it.
If you drive, you must test your blood before setting off and this, along with testing before (and 2 hours after) meals, means that you could easily test 10 times per day.
How often did your DSN tell you to test? If 100 strips doesn't cover this, ask her to contact your GP. Type 1 patients shouldn't have their strips limited. The hospital will be able to help you (either your DSN or consultant).
You have the right to attend hospital diabetic clinics, so don't feel forced to change to your GP's clinic.