a) On a flight say you depart Southend VFR for Exeter, ask Farnborough for basic service under VFR rules, if you later enter cloud (with an IMC rating) should you advise them from a legal and practical view point that you are no longer VFR and are now IMC and request a Traffic Service?
In Class G, you are not obliged to speak to anybody. But if you are talking to say Farnborough, you should advise them if you change from VFR to IFR (if say you enter IMC).
Whether it makes any different to them, I doubt. I have never noticed anything.
Sometimes, when ATC passes me traffic info, I tell them I am in IMC and they then sometimes stop doing it. But if I was getting a report of traffic at 1 mile on a recip track, I would request what used to be called 'radar advisory', now called 'deconfliction' I think, and this request is the only way the ATCO is permitted to suggest which way you should turn to avoid. They are not allowed to make any suggestions otherwise.
b) Enroute to Exeter, you are still in cloud and wish to transit say Solent zone, when you call them up although not on an IFR Flight plan do you state condition as IFR while requesting a zone transit?
Yes. In Class D, they apply different separation criteria to VFR v. IFR transits.
c) Should a transit be denied and you continue in IMC remaining outside of CAS you can if you so choose not talk to anyone?
Correct.
Just keep the radio tuned to some station, in case of having to make a mayday call
d)when you are then approaching Exeter and still in IMC would you advise again flight conditions as IFR even though not on an IFR Flight plan?
Yes.
And ask for an instrument approach (obviously).
IMHO, if you embark on a flight where there is a reasonable expectation of expecting an instrument approach, I would always phone the destination. Or file a flight plan. In fact one should always phone the destination, because many airports are PPR/PNR/all-kinds-of-crap-like-that. And the ILS or whatever might be INOP so you need to check the minima for the next one up against the actual/forecast wx, etc... airfield notams are worth getting for any serious flying, but a phone call is better
Thanks in advance, Flying in the US where none of this would be legal as an IMC rating does not exist has made me un clear about UK rules and procedures
Here, the existence of the IMCR and the ability to fly IFR in Class G non-radio, has made the whole subject of VFR v. IFR in Class G rather moot. You can depart (from a Class G airport) "VFR" into OVC005 and drill straight into a cloud. (Class D airports have VFR minima; typically 1200-1500ft cloudbase). In the USA they cannot bust you for not having an IFR clearance (not in Class G) but AIUI they can bust you for not having filed an IFR flight plan. Here, nobody cares.