This is one of the most confusing threads in a while!
Your budget isn't large enough for what your spec list is, 6 people in comfort, fishing, towing etc in a 4m new boat. That is 5m plus territory for 6 people and kit.
Why you are wanting new is beyond me tbh. You are only going to use it a few times a year by your own admission. The second you buy a new engine/boat you can kiss goodbye to 25- 30℅ of your money. Plus it will need 150 quid ish service each year to keep a warranty too.
New doesn't mean it won't break down, just means if it does you don't need to pay to fix it, but you paid a lot more money to begin with and servicing so factor that in.
If it was me, I would buy a decent used hardboat/Sib and if it isn't for you it will sell for what you paid give or take, buy something else.
I can pretty much guarantee what you buy won't be what you end up with in a few years so I wouldn't buy new as you have no idea what you need or want yet, no disrespect intended.
Be sensible, buy a good used 4m ish package and try it out I'd say, it is as close to a money back guarantee as you will get.
Oh, a used yam, mariner, Suzuki etc or a new parsun.......that is a no brainer, used brand name as plenty of choice.
BTW, pound for pound a RIB or Sib has to be one of the most expensive means of getting into boats, tubes are not cheap and need careful looking after. If you can store a trailer than perhaps the funyak or the terhi is a better get for you. If you need it to fold then have a look at f-rib, if you need to roll it up then check out the sib section for advice.