Normally we'd have gone with P&O Hull - Zeebrugge and return the same route.
This year we went out with DFDS Newcastle - Amsterdam and return via Eurotunnel.
Hull - Zeebrugge used to be considerable cheaper (I don't know about this year, I never looked as I wasn't going to be going with P&O), gave a shorter drive and an earlier start in Europe, the only downside being a longer drive in the UK.
You may already know this, in which case, sorry…..
DFDS Newcastle - Amsterdam sometimes have ‘specials’ buried in their brochure, with big savings. For example, one year, they had an offer of a camping holiday, which consisted of 14 campsite vouchers and a return ferry crossing, for only 50% of the ‘normal’ ferry fare. No checking if you actually camped, we used the offer to visit a friend in Sweden, and stayed with friend.
Although we live only 4 miles from the North Shields ferry terminal, without special offers, it is cheaper to drive to Dover or Folkestone and take short crossing or tunnel, particularly if heading south once across channel.
We normally use tunnel or DFDS Dover-Dunkirk.