Rupert S
Rather a sweeping statement if you don't mind me saying. There are times and places where you have to fly in IMC without a radar service. Outside of CAS this is a fact and there's nothing you can do about it. That's why there's such things as quadrantal / semi-circular rules - to reduce the risk. It's like I said earlier - you risk assess it and act in accordance with that assessment. It's neither good nor bad airmanship - just a fact of life.
IO540
Your instructor is technically right. Take a look at the UK AIP (AD1.3 is the relevant section). There it states what flight rules are applicable for each airfield, and any caveats that may apply. So - you can only depart and arrive VFR at some (mainly A/G / AFIS type airfields). The grey area is - at which point can you declare yourself en-rte and therefore go IFR
To be quite honest this table should really be re-labelled VMC/IMC because, as others have said, what about night flying, which is technically IFR (but which uses the 'clear of cloud and in sight of the surface' caveats of IFR at airfields which are not listed as IFR airfields!)