Can any body help and give me some advice.

Took boat out for my first sail, and all was fun, but noticed a small leak, which came a 'bigger' problem as I put my foot on the 'plank' above the leaky joint.  The joint between two planks has come apart, and I now have a nice 2ft 'hole' where the joint is.

How is the best way to repair, and what glue, and how do I clamp the planks together.  Is this something I can do

Any advice welcome.

If it is just a cracked glue-line, try Zap CA which is a penetrating grade of cyanoacrylate adhesive. Run this into to crack and it will fuse with the old marine glues. You can buy it on line or in model making specialist shops.
Be careful as this is a superglue. It will run everywhere and glue you to the boat quite easily.

It might also be worth pinching the joint up with s/s countersunk screws.

dry it out, clean /sand old glue off. Epoxy joint back together and use 6mm scews as clamps. You may need to heat screw driver up with heat gun to get screws out once set. Fill screw holes and refinish.

In some cases you can avoid screws and clamps, and just press the joint shut by wedging a piece of timber between the floor of the garage and the hull. It is a delicate balancing act though, so take care that everything will stay in place. You may need pressure from the inside too; perhaps wedge another bit of wood between the plank and the other inwhale, perhaps with a bag of bricks hanging off the middle.

For a midships leak (which is where it usually is) and with the hull inverted on supports & C'board removed, I constructed a kind of external frame using pieces of timber jammed in the case, others clamped to the gunwhale, and yet other pieces G clamped between them, and then use short pieces of timber to apply external pressure at the right places. You also need internal pressure points, with luck against case or opposite gunwale. Sorry, no photos.

It does take a little bit of time and ingenuity to set up, but you don't damage the hull by screwing into the lands.

Had the same problem with 1074.

With the boat inverted I opened out the broken glue joint and held them open with dowels. Then put a thin saw blade through the joint to remove any old debris/glue and allowed the whole area to dry completely before filling with epoxy and fibres . 
To keep the joint contact good, I set up a support from below and then screwed at approx 6" centres until the glue was set. Removed the screws and then filled again with epoxy. 
It seems to have worked.
I'll send pictures direct to you, as I can't seem to manage the attachments.

Yes, temporary screw then fill in is OK on painted hulls and much easier; my screwfree repair was on 1620's varnished bottom.

Here are Richard Steven's photos of repairs on 1074.

Cleaning the old joint is essential and you may find that the glue has failed further than you either imagine or indeed hoped.  Once it has all been cleaned out and well dried it is a good idea to put a line of parcel tape - the brown shiny one on each side of the new glue line inside and outside the hull - it saves the glue going everywhere.  Furthermore if you don't want to leave countersunk holes in the outside of the hull I have found that a good idea is to get a batten width of 4 or 5mm ply and sheath it in the parcel tape - shiny side outwards.  Then when you screw it through the ply and the lands use a stainless washer against the screw hole.  You will get a much neater hole on the hull and you don't run the danger of the screw going into the potentially soft land and out the other side ie a hole right through the hull.  When you unscrew the whole thing when the glue has set you will find that the covered battens just lift away as the glue won't stick to the shiny side of the parcel tape.  As regards heating the screws if they are a bit stuck in, a bit of heat on the head with a soldering iron very quickly softens the glue.  Similarly a warmed sharp chisel allows excess glue to be removed when it has set followed by the usual sanding and sanding and sanding .......

Cheers everyone for the advice.  she's fixed. Had a pleasant potter in very light winds.  

I screwed and glued the joint. ATM I have left the screws in and made smooth on the bottom. my thinking being that as I dont know the extent and concern being that as I dont thave any 'speaders' on the hull where it split, thus the screws would give a bit more strength to the repair. I am lucky that the hull is painted on the outside so the heads are invisible.