"my point is that 26 key lachenals are the best value for money."

Well, that rather depends on what you want your instrument to do. My first Anglo was a 26-button Lachenal and, although it was a nice box, I traded it in after a couple of years because it didn't play the chords I needed. I'm not aware, BTW, that 26-button instruments are especially common. There is just one 26-buttoner, a Jones, on Ebay right now, key unspecified, current bid very low, but billed by the seller as a "restoration project". There's also a 30-button Lachenal needing a lot of TLC that might be a better bet for the would-be-repairer.

"alternatively get a 20 key dg lachenal they are not too common but they exist, the advantage of this is that you can play irish music on a dg 20key"

Apart from the fact that few Irish concertina players favour a D/G instrument, our OP Matthew has not said at any point that he wants to play Irish music. He has said he likes to accompany songs.

"30 key accordion reeded concertinas sound like accordions"

I've played several Morse instruments and (speaking as one who usually plays a beautiful 100-year-old Crabb) they sounded nothing like accordions. IMHO the sniffy attitudes I sometimes encounter about 'hybrid' instruments are, more often than not, pure snobbery.