On the right hand side of the plunger container there is a U shaped pipe
with a flattish top. The other end of this pipe is connected to the bottom
part of the reservoir where an approximately 1 foot pipe connects to the
back of the actual toilet. My question is can I still get new siphon. There
is one on Screw fix looks something like it
http://www.screwfix.com/sfd/i/cat/95/p2635095_l.jpg
Is it lightly to fit? both pipe sizes and physically in the reservoir
changes and I'm stuffed?

I fitted one of these recently, and with one proviso it went surprisingly
easy (i`m useless at DIY too). For the same of the couple of quid it`ll
cost you to have a go, its worth a shot :-p

The proviso is the black bits shown on the main "tank" of the siphon -
they don`t hold in place of their own accord if you want to seal the top
one to have a "bigger" flush - I just used a but of black insulating tape
in the inside over the hole, and kinda wrangled some around the outside
to make sure the black piece stayed in place, and its been find for
several months.

Lastly when I replace the siphon am I lightly to need any other pieces such
as a WC Pan Connector Straight

I didn`t have to - the bottom of the siphon has a seal that my flush pipe
went into just fine.

Incidentally, the other reply mentions water levels - in my case (sounded
very much like yours) it was the plastic membrane that had fallen apart -
as you pull the handle it lifts a rigid inverted "T" shaped piece of
plastic, and above that within the main body of the siphon is, for want
of a better word, a piece of cheap sh!t flexible plastic, which initially
"blocks" the main body of the tank to move the water over the top of the
siphon, then flaps out of the way once the flush starts.

--
Please add "[newsgroup]" in the subject of any personal replies via email
--- My new email address has "ngspamtrap" & @btinternet.com in it ;-) ---