You've got to think - what does your current van not do, that a new one will? After a few months, the honeymoon period will be over, it'll drive a bit nicer and be a bit cleaner but will essentially be doing the same job as your old van.
We had the same dilemma with our car, we had a 2014 Captur Diesel, never gave us any problems but was looking a bit run down. Wife wanted a shiny new(er) car, so we bought an Audi Diesel, 2021. In the first 3 months of ownership, the Audi has given us more problems than the Renault ever did (luckily all fixed under warranty). The sound system is better, it's a bit quieter and obviously looks better inside. But that's it. We still use the Renault for school runs, taking kids to Rugby, and taking stuff to the tip, because we don't want to get the Audi dirty. So it's basically a luxury, not a necessity.
£400+/month for a "nice to have" or a luxury would be a lot of money for me