As soon as a controller says "Ident", I push the button immediately and usually he says "Radar identified" at the end of his message, before I've even responded.

Chevvron,
Firstly, thank you for all you hard work at Farnborough Radar. I hugely benefited from your service when I worked at Denham a decade and a half ago - I was working the first morning of the change to Basic and Traffic service.

With all due respect, the current edition of CAP413 generally advises on first contact to give callsign of agency, then aircraft callsign, then initial request. On page 24 of Chapter 11 'Phraseology examples' Figure 26:
.Wrayton Information, G-ABCD, request Basic Service
again on the following page Figure 27
Westbury Approach, G-ABCD, request Traffic Service
There are numerous other examples through CAP 413 where the initial call is formatted like this.

You're absolutely right that the pilot shouldn't launch into their complete message (as I had one slightly nervous student do the other day, before I could stop them - the controller handled it with aplomb). However, a short introduction of what you are wanting takes up little air time and gives the controller an expectation of what is to come.

Incidentally, to answer the OP's question, CAP 413 also says the response from the controller should be simply 'pass you message' and the squawk instruction should come AFTER your detailed message, so you shouldn't have to be fiddling with the transponder until you've got your message out.

TOO

I think I would go for option 3 of the OPs list...
Reply.. '' G-CD squawking, 1,, 2,, 3,, 4,, Request zone transit at 2000ft. '' ( Press each key as you call out each number.)
The bit about having to fly the aircraft should have been settled 10 minutes ago; By either engaging the auto-pilot, or trimming the throttle and trim wheels, to make the aircraft aerodynamically stable, for straight and level flight.
It is always good practise to only give up to three pieces of information in each radio transmission.

I actually retired from Farnborough slightly before the changeover from FIS/RIS to TS/DS in 2009 however I did participate in a 'workshop' at the CAA in London in early 2008 where the details of the proposed 'new' system were discussed plus during that time and for some time after retirement I attended UK Phraseology Working Group meetings at Gatwick.
At that workshop, I got the distinct impression that it was 'controlled' by the military element of the participants so there was little difference between the 'old' and 'new' services.
I and at least one other person tried to 'push' the idea of moving back to the 'original' system (and was firmly put down) of using radar as part of the Flight Information Service as notified in ICAO Doc 4444 para 8.11 which was used in UK airspace up to about 1978 and which I understand is used as 'standard' in much of Europe but I got the impression the decision had already been taken before the workshop and was not to be changed, hence we ended up in the present situation.
At least I was able to launch the concept of expanding LARS coverage to the volume of airspace under the LTMA covering the areas around Denham and Elstree; I did used to operate from Denham at one time but due to the then aerodrome operator objecting to my participating in an interview with AAIB which didn't leave his operation in a good light, I switched to flying from Blackbushe.

I too was part of a meeting to which the CAA proudly introduced the upcoming new 'Basic/Traffic' system. Apart from the expected range of queries and criticisms we were to a man and women astounded that the UK intended to introduce a new unique service, which was to be completely at odds with our increasing integration with EASA land. The mood in the room was the same; why seek feedback when minds were already set in stone.

Down in NZ setting a code is redundant.
I first establish contact.
Then pass my position/level and the request.
If it is available the clearance is in the response.
No setting a squawk, squawk ident etc- we are ADS-B compulsory.

Hi Maoraigh, I suppose you do get some turbulence from those hills in Scotland.
The only snag with setting the squawk first then calling, is that if you are flying in the Midlands area, you will get stepped on by two or three other aircraft, and it might be about 5 minutes before you can read-back and confirm your squawk code. Some pilots have no SA on the radio, and just key up asap.