update: not much progress- been under the weather with man flu.
However, I am feeling pretty good today about my very mediocre DIY skills.
The last pic above shows where the dining room floor ends... I had to cut the planks longways to fit to the then dining room wall, so all tongues cut off.
Now, I want to try a no threshold transition, and it's been difficult to get a result. Biscuit jointing has been mentioned etc.
Anyway, today I did a test on the old flooring, to cut a line longways at about where the tongue would end, and then prised off the bits above and below the tongue. Yay!
Then, No Yay, the new board's groove won't slip over the tongue. Damn!
I had a go at a tiny rout out of the groove on my table router- it worked! Yay again! So now I've cut the 3m 30cm length of the last row of boards, exposed the tongue all along it with a chisel (it was easy really), and am ready to rout the 3 boards for the new first row. Feeling smug (it won't last).
Will post a pic of the transition when done.