Hi Paul I recommend something similar to this......
http://pages.ebay.com/link/?nav=item...000822&alt=web Aldi had them last week about £29.99 I bought one from lidl about 3 years ago for a one off job for a customer I think I had to cut some rot out of huge barn doors and I thought if I can get in with that it will save taking the doors off which it did. Since then it has become one of my most used tools I even run it off an inverter in my van to slice ply up from the merchants so it will fit it saving taking a trailer or tying on the roof.its also the most borrowed tool by my father and brother tool. Perfect for your paneling jobs (the straight cuts anyway)you can use the side fence if close the edge or free hand or clamp a straight edge on the ply and run down that. Mine cuts ply upto an inch with a very neat finish well worth £30 if they have any left you can adjust the blade depth to cut a groove too. I have a 6" and 9" circ saw and rarely use them now. Once your cars on the road I thoroughly recommend getting yourself a sewing machine and having a stab at the tonneu cover and trim parts yourself my sewing machine is now my favourite hobby in fact I been sewing since 6am today which is odd when I used to do off road trail events on Sundays. My heavy sewing machine was a £23 eBay Christmas bargain thread is £5 for a big spool of rot proof bonded nylon and I pay £75 for a full cow hide or £10 a meter for 1.5m width of a 40% leather faux leather material which is really good I may do my van seats. Most canvas or waterproof heavy materials are under £10 a meter and I think you would really enjoy it and you would also of done everything on the car I learnt everything off you tube. Keep it up looking good Ed.