Battens and secret nailing are only going to increase the height which then makes the transition to tiled area even more problematic.  What is the parquet laid on top of?  Not timber, at a guess.  If so then adhesive is your best choice, I reckon.

As for the transition strip, I can't really help as whenever I need one I simply make it up to length, height and profile in my workshop.

Bit of a long one, any expert layers of wood flooring please bear with me.

I have a job where I am laying a solid wood floor on an old parquet type floor. (My client doesn't want to restore the parquet to original condition.)
The room is a square shape and a corner will be tiled as it will be used as a kitchen.

Can anyone with some knowledge of laying wood floors give me their thoughts on the best method of laying it please. If it weren't for the tiled section in the corner of the room I would lay a dpm and lay the wood onto adhesive underlay, although since the wood floor is going to end in the middle of the room and swap to tile I don't trust the adhesive underlay to be strong enough to hold the last row of wood never mind for years to come, especially if footsteps will be crossing over it regularly to reach the kitchen space. With this in mind I am thinking of laying it directly on a flexi adhesive (as recommended by a couple of flooring companies).
I was set on this last option although now I'm wondering if batons and secret nailing would be a good idea instead. Can anyone give me their thoughts on what's the best method for a lasting finish, adhesive underlay, adhesive direct or batons and secret nailing?

My second question is about where the wood section swaps to tiling. I need a long reducer but the only reducers I've seen so far have only been up to 1m long for use on door thresholds; I need something longer as where the wood floor will meet the tile floor is in the middle of the room and the edge runs for a few metres (3 I think).  I imagine using 1 metre long reducers end on end would give a poor looking effect. What is the best thing to use here? Is there such a thing as a long 3-4m long reducer? I've seen wood floors reduce to other floors in this way looking fantastic when done well, sometimes with an octagonal edge to give a decorative finish to a square edge and I think it looks really smart. I'm looking for a classy looking finish - what's the reducer/trim that I need for this please?

Many thanks for any help.

R.