OK - Change of mind...
I have just done a spreadsheet (whilst bored on the train) of monthy running costs over 2 years for a variety of options from getting the phone from EE (but paying the higher upfront) vs getting a genuine UK Note 3 and a SIM only deal on a similar tarriff.
It seems that with EE, paying the highest upfront cost for the handset (about 60% of the independent price) is about £16 per month cheaper than buying the handset outright and then buying a comparable EE SIM only.
I seemed to have debunked the idea that "it's cheaper to buy the hansdset compared with going on a plan" - at least for EE. I can put the spreadsheet on GoogleDocs if anyone wants to check.
The range I was checking in was "10GB per month data with tethering allowed". The plan gets me 10GB on 4GExtra (that's super fast where available). The SIM only gets me 8GB per month on 4G (ordinary, not superfast).
The Plan requires 2 year lock in, the SIM only is 1 year (1 month available for more money). The calculations assume a 2 year amortisation period.
To be fair, repeating the same exercise with Three, it is cheaper to by the handset outright.