If OD was a good way to go, I would have done it by now. It's not. If your using NHS doctors, they will get wise to you thanks to the new NHS databases which tell them how many times you see a doctor, what meds you get prescribed, they will know what your up to. It doesn't matter how much 'shopping' you do, they all know who you are from your records, which are stored on the database. Changing surgeries won't cut it, sorry.
Like Lena says, think about the doctors and how they will feel knowing they prescribed the meds you OD'ed on. I spose your also being dishonest about WHY you want the meds, and I don't think you'll get anything from an NHS doctor that would work in OD anyway. They don't often give those kinds of drugs out apart from in extreme curcumstances.
'Doctor shopping' is also a criminal offence in some countries..