Understand that NHS support is insufficient in many cases. It's total pot luck as to whether you get a midwife/health visitor who even understands breastfeeding, let alone has the time to actually properly support you.
If there's a suggestion of a tongue tie, it's usually the case that there is one. I have no idea why some HCPs are so insistent that if they can't see it it definitely isn't there, it usually helps to have it cut. Tongue ties are hereditary so if your first had one it's not unlikely your second will as well.
I would strongly recommend getting in touch with a breastfeeding counsellor (NCT, ABM) or La Leche League Leader, or Lactation Consultant (Google IBCLC search UK) and see if they are willing to offer you a debrief session where you try and figure out what the barriers were last time, and how you could overcome similar issues if they happen again.
And yes if you want to use a dummy, use a dummy. They can be a risk in certain cases and shouldn't be a blanket recommendation, but in most cases it will be absolutely fine. I wouldn't use one if you're having latch issues as it can exacerbate this, also a very sleepy baby who is potentially not getting enough calories because they don't have the energy to suck effectively should not be wasting sucking energy on a dummy. (The caveat to both of these is if the benefit - e.g. to your sanity - outweighs the risks - choose the dummy). And don't underestimate the importance of comfort feeding - despite what some books/people say, those "fluttery sucks" once you get past the initial strong drinking are still beneficial both for your supply and in terms of the baby getting milk while they are doing this. Sometimes you can be given the impression that the feed is of a limited amount and once they have drunk that amount there is nothing there but air! Not true - allow that comfort/fluttery sucking to continue whenever you have the opportunity to. Which is not the same as needing to do it every time. If you would rather put the baby down and have a shower or play with your older DC, that's fine too.
Consider/read up about safe co-sleeping and look into getting a cot that attaches to the side of your bed. IME absolutely essential for surviving newborn BF.