Hey thanks for all the good feedback, my shoe string is around £500 quid at the moment ,

The reason for pen plotting is because the type of shapes i am interested in cutting are to be faired on the job (clinker boat planks).

Being able to draw on an 8x4 accurately has great DIY potential for allot of budding designers, you also have the option of plotting on paper laid onto the sheet, this then allows accurate patterns for cutting out all kinds of materials, im an upholsterer by trade and have sewn up anything from car headlinings to tents, boat hoods bla bla , i work in the furniture industry where allot of money is thrown at big cnc kit often burdened by service contracts and sytem updates, cat and mouse situations with sofware compatibly, Journeymen asking why they cannot just pick a hand tool up and crack on happens too. extraction of cad patterns and lines into the real world is more the issue for me, i can see low a cost cnc plotter going into all kinds of projects and small business solutions allowing the craftsman not be be burdened with the chance of
measurement mistakes.

Funny enough i have too considered image projection but came to the same conclusion about scaling and accuracy.

I have one last idea id like to put forward that may keep the cost down if only i knew how to achieve it , how about a small robot plotter that runs over the surface on a sheet , although you would have to lay you sheet down it would perhaps be compact and portable! so the sheet could be anywhere temporarily , onsite cnc plotting for builders shop fitters now there's an idea!
Printing out detailed lines onto floors..

Could i convert an old scanner to move and draw lines perhaps.

Thanks guys for all the advise, its good to purge the mind of mad ideas!