The best dashcam out there seems to be the Nextbase 512G from all the research I’ve done, and infact I just bought one. They seem to be one of the few which works at night, in bright sunlight and shows numberplates properly which is a big headache with some of them.
Currently available from Amazon for £150 and Ebay for £142. You do also need a 32GB Class 10 Micro SDHC Card as for some reason it doesn’t include one, even a little one.
Can’t help however with the DVD problem, but you can buy fairly cheap DVD players although finding one that charges on 12v and 24v is something I’ve not tried.