Budget change around

I've had a re-think of my spending process this fortnight and I've decided to trial a cash envelope process for my "non bill" expenses. I'm going to keep cash envelopes of how much money I've allocated to food, entertainment, health and beauty and gift expenses. All my bills will still stay in their usual bank transfers but I'm hoping this new process will help me get more of a handle on my expenses so I can limit the overspending. I went to

I've done a rejig of this fortnights budget as well to factor in my medical bill and also some extra entertainment expenses because my best friend and her boyfriend are coming down for the weekend and I need to do the tourist thing and show them around and that's going to cost me. I've also allocated a gift expenses fund because my work loves birthdays and nearly every week we get called on to "donate" money to presents this past fortnight I've been paying my donations with spare change I had in my drawers and not allocating it to my spending, but it's time to factor this into my expenses.

I would just like to note as well my rent is paid monthly but every fortnight I need to allocate the money out of my budget to make sure I don't spend it!

250	credit card
586.5	rent
100	parents
49	internet
42	gym
40	phone
25	electricity
25	house
60	medical bill
100	savings
120	food
50	entertainment
20	gifts

I was only planning to keep only the food, entertainment and gifts in cash however when I went to the ATM today I failed at maths and withdrew $210 instead of $190 so I'm still tossing up between going to the bank and depositing the money back into my account or just keeping the $20 in a cash envelope for the house fund category.

The one thing I am unsure about is how will I be able to snowball any unspent money from these envelopes? Do I keep the money in a jar and deposit back into my bank account when it gets big enough our do I cary it over to the next fortnights envelope? Has anyone else had any success with the Cash envelope system? Does anyone have any feedback or advice?