The one-off connection charge isn't really a problem, being a one-off.
My my calculations Vodafone would cost £28 x 18 + £49 + £6.99 = £559.99
Plus.Net = (£18 + £17) x 18 = £630 (assuming the worst case discount - will need to give them a call to see if anything better can be done).
So there could be a saving of around £70
The main problem (well, the only problem) with Plus.Net is the continual line rental increases
I just worked out over 12 months, going to Vodafone would save me £6 a month or £72 over the year. So not too bad. that is including the £1 more i have to pay to Plusnet from next month. I am also working on the 38Mb/s speed and that I am already with vodafone for my phone, so my bill get reduced again. it would be £3 a month more if I was not already a Vodafone customer, That then would almost know the savings out over the 12 months.
If I went over 18 months whihc I should have I suppose then I would save more.
You said about Plusnet putting line rental up, but there is nothing stopping vodafone from putting their prices up and after 18 months they could hike it up a fair bit, so it would be possible to change networks again, but I am not sure if I can be bothered to do that and the risk that something could go wrong and I have no internet.
My problem with Vodafone is their customer service stinks and just because their broadband customer service is separate at the moment do not mean it will stay that way, not enough people with them to have any decent reviews, using your own router is hit and miss.
the other problem is would they want me to re-enter into a contract mobile phone wise as I am almost out of contract and what would happen if I decided i did not want to use their mobile network if they did not force me to re-enter into another phone contract?
Also, I am not sure if I really want to enter into another long contract.
So many things i need to look at.
I do want to cut down on things and sty and save money, but not if it locks me in and offers a worse service than I am getting now.
Desktop machine now powered by windows 8.1 pro 64bit, no dreaded metro, laptop by Linux