I have to wonder if those who are so critical of the Wren plywood canoe have actually paddled one. I'm not 100% certain they are wrens, but do look like it to me.
Sure the course could be a bit cheaper, because (a) I'm a cheap skate. (b) you can buy better boats for less, but I think it could be a very satisfying and worthwhile experience. For your £700 you get a long weekend in which to build a perfectly usable boat with all the components sourced for you. You then get to build your boat while supervised at a client/instructor ratio of three to one. Like this you should be able to create a pretty good example of a Wren rather than a "Reg Prescot" job! You should then have the experience to try something more complicated with a better hull shape later on if you so desire. Lets face it though, folks are being critical about a weekend canoe building course at the end of which you get a canoe. This on a forum where people regularly pay several hundred pounds for the latest Mors Bear-Mears bushcraft knife which then sits in a draw never to see daylight again!
As to the performance of a Wren, well, they are quite capable simple craft. Perfectly suitable for bobbing about on Ullswater or Loch Lommond or trips on grade I or II rivers. For sure, they don't have the lovely lines of an E.M. White or Atkinsons Traveller and you'll not be making fancy freestyle moves in one. They are surprisingly resilient though and with a reasonable maintenance regime will outlast any plastic boat.
I don't recommend any of the poly boats to people simply because of the weight. If you're spending hundreds of pound on a plastic boat, wait a little longer, save a bit more and get one of Royalex, you'll not regret it. Saying that, my Penobscot 17 was bought in '89 to replace the Colman 15 in Ram-X I had, the miles we've since covered can now be counted in a four figure number, but I don't see her out lasting the plywood sailing dinghy I have which was built in 1955!
So, all in all, I'd prefer it to be a little cheaper, but it would be good experience and you'll end up with a nice functional canoe that will make you smile every time you portage with someone with an SP3.
Al