2nd language v. of site - new domain or append existing?

[Fitz]

I have a client (accountancy/tax advice) who runs a .co.uk site (in English) and is keen to start to target French speakers too (whether in France, UK or elsewhere).

I had some luck a few years ago (different client) simply appending some French language versions of the existing English pages to the site. So index.htm might have become index-fr.htm and so on (or perhaps all French pages could have gone into a /francais sub-directory). Each page was more or less a straight forward translation of the original English version so while strictly speaking the two shared content, duplicate content was not at that time an issue due to the change in language. So, Google had no problem picking up either version when either French or English was used in the query.

My question is this:

From a traffic/ranking point of view, is this the best way to have a second language, particularly in the short to medium term?

I suspect that the answer for the long term would probably be to have a .fr domain separate from the co.uk domain ... but of course that means doubling up all the link building work (which is lots of work, would take a long time and so would not be my first choice due to the extra time it would take to start ranking/working).

Any thoughts welcome! Thanks in advance.

[Fitz]

The previous thread ...

Multilingual websites and internal link structure

... seems to have discussed quite a lot of the issues. But ...

I felt that the question of whether or not to host a French translation within a section of the existing (e.g. .co.uk/fr) site - or whether to host a French translation at a new .fr French domain was not agreed unanimously.

Therefore any extra thoughts on that aspect not already covered in the above thread would be appreciated, particularly in view of the fact that we are targeting French speakers IN THE UK more than we are targeting people actually in France. (So .. hosting any .fr domain actually in France may not be such a necessity, if we go the way of a separate .fr domain - or do you disagree?).

Other questions spring to mind:

Is building links for a new (.fr) domain harder (in terms of gaining in the SERPS) than building links for a sub-section of an existing site? The new domain Sandbox period combined with a bit of linkjuice from internal links would suggest so, to me... but is the long-term ranking potential better for the separate domain?