Mobile phone - any good deals coming up?

[Beggarall]

My contract with Vodafone is expiring - says I am entitled to an upgrade. I have found Vodafone expensive, does not give good local (to me) reception and do not give any rewards for customer loyalty. The "upgrade" is going to cost more than my current basic contract which is £47 pm. Their overseas use is also expensive and (as I have just found) the merest touch of the phone to get e.g. voicemail incurs significant charges. I am looking for iPhone 6S with good UK package, reasonable internet use (more than 2Gb) and favourable use abroad. Are there any good packages out there - or maybe coming up for "black Friday"? Help please

[Beggarall]

Thanks for the replies - I will certainly look at Three and will enjoy a further conversation with Vodafone Customer Care! I think the World traveller costs are expensive - and considering we are abroad quite a bit these days, £5 per day translates into £150 per month! i only need this to receive urgent messages/texts from the UK as most places have reasonable wifi access these days. For a prolonged trip it is better to buy a local sim card. Will be pleased to hear any more views. Thanks again

[Beggarall]

I have had my first contact with Vodafone customer care and a lovely helpful call-handler (for a change) - maybe because I pressed the option which said "planning to leave Vodafone" or something similar. They can't offer anything much on an iPhone 6S because they have tied themselves into some resale agreement (?with Apple) but can offer a 6 with unlimited calls/texts and 2Gb data for about £30 pm with first month free. No deal on overseas use though. I see EE have similar deal offered for £24pm and £60 upfront for 6S. Looks like a tour of the high-street retailers next step. What about Carphone Warehouse? Is the iPhone 6S much better than the 6? The quest continues

[Beggarall]

Bringing back to the top....I have been continuing my search with now just 4 days before I have to hand in my notice to Vodafone. I can't find any mega-deals. Most will routinely offer unlimited calls/texts plus 2Gb data. EE seem to have the best coverage and have been the most competitively priced - about £37 pm for a 6S and 24m contract. You can actually do a bit better than that buying at Apple provided you pay an amount up-front for the phone (varies). I am getting tempted to buy a phone outright and then take a sim only contract. Apple 6S = £539 for 16Gb (is that enough memory?) which works out at £22.50 per month over 2 years plus sim only contract at about £12 pm - total £35. So minor difference but the ability to change sim as needed. Still thinking about this but my questions today are:
1. If you change your sim provider is it easy to retain the same number - I know they have to give the PAC number - but is this easy in real life?
2. If you have an Apple phone bought outright and then decide to take a contract, does that lock your phone so you can't change sim while abroad?
3. If you do use a foreign sim while abroad, can you set up call-forwarding from your UK based contract provider?
4. Do Apple phones bought in the UK work OK in the USA - I have heard there are some differences
Thanks for your help

[Beggarall]

Thanks GreigM - really helpful

[Beggarall]

Quick update. Further discussion with Vodafone Customer Services to explore the options - it is amazing how there are all kinds of permutations that are not immediately obvious and very difficult to navigate. I have agreed to a SIM only deal for £15pm for 12 months which gives unlimited calls and texts plus 4GB data plus use in EU without extra charge. Plus some sort of entertainment package for 6 months. Need to change contract before it ends because otherwise price will go up!! Can use any phone and will purchase a 6S at some point but meanwhile retain my 5S which I will then unlock and use for travel further afield. Overall much better than I am paying at the moment and gives me much more flexibility without the hassle of PAC numbers etc. There maybe better deals out there but this is the most convenient for me. Thanks to everyone for their input.