I can create this on my modern UK keyboard with Ctrl-Alt-4 but before I purchase a UK layout model M or Unicomp I would like to know if a Euro symbol is possible as I use it a lot?
Definitely, as the keyboard isn't responsible for creating the Euro symbol with newer keyboards. The "scan codes", which tell the computer which key was pressed, were not changed when the Euro symbol was added: only a keyboard layout table in the computer, which it uses to convert scan codes to ASCII (or ISO 8859-1 or Unicode) characters was changed.
Some U.S. layout keyboards have a Euro symbol printed on the number 5 key, but whether you have one of those or a Model M, you would not be able, normally, to use Ctrl-(Right) Alt-5 to generate it; there, you have to select the "U. S. International" keyboard layout. Once you do that, again, it works equally well whether you have an old keyboard without the symbol on the key, or a new one.