The chassis features an integral roll bar but these need to be braced to be of any real use. Fisher Sportscars sell a removeable cross bracing kit, but these are a serious pain for the passenger as they are just in the wrong place for their feet.
Bought some new Hella, Ford Escort RS Turbo replacement twin-tone horns on Ebay for a very little. These should be loud enough.
The odd track day is inevitable with a car like this. I've seen and heard of so many that have gone up in smoke from oil and fuel leaks. For the sake of a £100 or less, it's a no brainer to install some sort of extinguisher.Rally Design do a Lifeline Zero 2000 (model no. LLS0026C), mechanical, 2.25 litre system for £85 which looks like the best bet. I've seen a few people that have mounted plumbed-in fire extinguishers in the empty side-pod. These means it doesn't clutter up the passenger footwell. I'm planning to do this myself. One advantage of putting it in the side pod is that the mechanical operating switch can be conveniently placed within reach of the driver and mounted within the right pod shelf.
Paint all your safety related fasteners "Blue" once you've torqued them up. That way you know the job is finished, if you then have to remove and refit the fastener for any reason change the colour to "Yellow" to show that is been removed and re-torqued. Looks good for the SVA too!