The callsign has to be transmitted at the beginning of a message.
Yes, when you initiate the communication. The readback ends with call sign.
A correct readback should end with the callsign.
That’s what I learned 20 years ago. Good to know some things do not change 
What’s with the “In the box” thing? I’ve never heard that.
I’ve been getting 1000 more often in France, departing from Paris or the Nice region, interesting to know it’s connected to Mode S and primary.
I always get a squawk change when talking to Basel on the way to/from the south of France over the Alps.
I learned 29 years ago that on an answer to ATC you ‘sign’ your message with your call sign.
I learned 29 years ago that on an answer to ATC you ‘sign’ your message with your call sign.
Same here 31 years ago 
What’s with the “In the box” thing? I’ve never heard that.
Indeed some pilots use it. I never liked this expression, it is so much aviation slang, same like “coming down” (for squawk number). Just reply the squawk number and that is enough. Pointless words on the airwaves like the “this is” that many pilots add before their callsign when checking in a frequency. How “could this not be” since its you checking in with your callsign !
IMHO only numbers and aviation words (Flight Level, Heading etc.) matter in clearance/instruction readbacks, absolutely, nothing else.
as I was flying 35 years for LH I can reassure both parties here that it is practice to either place the callsign before the message/readback or after it. According to personal preferences and may be short term memory capability. What Next however is right in saying that someone out of the Airbus Switching Officers Brigade, most probably an “Abteilungsleiter” tried to establish that more time to dial in and read-back procedure. I heard about that.
“Coming down” or " In the box" is somewhat disapproved as blabber …
I agree with Petakas – there is no place for nonstandard terminology. In the UK it’s OK, to a lesser extent in Germany, but elsewhere (France in N Europe, or anywhere in S Europe) they will quite likely not understand it.
And the standard ATC procedure in some places (Spain) is to ignore the radio call because that leaves no evidence on the tape that the ATCO did not understand the “conversational English”. So you get nothing out of it and have to say it again – if it is something you actually want e.g. a climb to remain VMC.
tried to establish that more time to dial in and read-back procedure
Should one not
I’m French but fly in English. I’ve never had any trouble being understood in English in France or Italy by ATC. I keep to standard phraseology. I don’t see why ATC outside of Britain should be expected to understand non standard terms spoken at a conversational speed with a British accent.
Britons seem to believe the rest of the world speaking English means they should be understood everywhere without any effort on their part. There are many forms of English however, and the one spoken in Britain isn’t the most easily understood version.
Britons seem to believe the rest of the world
I believe this is more or less true for all native speakers. Frenchmen are pretty much the same when speaking to non-native French speakers.
I’m French but fly in English.
Interestingly I came across a document by the DGAC the other day, might have been on this site in a different thread about FCL.055, that stated that French pilot’s were expected to speak French, but English was acceptable for training purposes. Good grief.
