Self Employed Courier driver....best way to buy a car?

Courier_man

Hi

I'm a Self Employed Courier driver. I work alone and use my own personal car for deliveries. I'd say I use the car for 80% Business and 20% social

I need to find a more efficient car, I have two options. Firstly convert my current to LPG or secondly purchase a Diesel.

I've been told because I'm self employed I can add a car or LPG conversion to my list of expenses for my tax return

The LPG conversion costs £1500. The Diesel I might go for is the 1.9 CDTI Astra for around £10,000, which I'd pay on finance monthly.

The questions I'd like answering are:-

1. How would this work? How much money would I get taken off my tax bill for the LPG conversion and Astra Car

2. Whats the most cost effective way of me buying a new car for work?

Thanks I hope you can help

I've see similar threads but didn't quite get an accurate answer. As most people use the car for the odd journey, whereas I'm using it for the majority of time for deliveries