most 'monthly' medications are given for 28 days rather than a calendar month. if you work it out, you actually need 13 prescriptions over a 12 month period, making a grand total of £96.20. an annual pre paid prescription thing costs £98.70 so it's costing you only £2.50 extra. if you need only one different prescription over the course of the year, say for antibiotics or something, then you are immediately better off (assuming i've done the maths right).
my doctor gives me 3 months (or rather 3 lots of 28 days) of the three medications i regularly take. i put a prescription request in yesterday, tomorrow i will pick up one prescription from the surgery with 3 months worth printed on it, take it to the pharmacy and come home with 3 months of meds. no problem.