The accounting package at the heart of it is Xero - a brand I had not heard of before. You could try the Xero software for free to see if you like its approach - but it seems to be able to deal with € and $ as well as £.
The benefit of having an accountant on board when you start should be that things get set up properly. It ought to impress prospective clients too that you are well managed and regulated even if small. That does seem to worry some transferring clients that have been used to the apparent re-assurance of big firm providers.
This type of product could also be beneficial to not so solo firms too. If anyone has has experience of cloud based book keeping or dipped a toe in the water please comment. What do you see as the risks and benefits of this approach?