Security for your mk1

How do you secure your mk1s as the factory door locks are like a knife in chocolate. I know I could change that, but what manual locks do you use and can you recommend any immobilisers that can be retrofitted. I had a system in my mk2 where you had to hold up the key ring within a certain time period to demobilise the car. 

Any recommendations welcome and something I could possibly wire in myself, manual locks that take into consideration the large steering wheel as well.

Cheapest, Pull the Fuel Pump relay.

Second a 9mm.

My favorite window decal:


 

Disklok is reportedly one of the most secure physical anti-theft devices, but pricey and cumbersome

2nd for Disklok

Had mine for 20+ years and although it looks a bit battered it serves well as a deterrent. 

The idea is that thieves will look at it like a "too hard to do" and go elsewhere. Job done for you, maybe not for someone else!! 

It is cumbersome but it will fit under the front seats and not slide around. 

Cheapest I could find…. 

https://ebay.us/m/xEi5d5

Had my disklok many years,  will use it again if i ever get the golf going. How ever if the car is targeted so they know its fitted, i think with the variety of battery powered cutting tools available it could be removed if with some noise