This app was mentioned in 2 comments, with an average of 2.00 upvotes
Tesco Calling Card app.
Any top up means you get free worldwide SMS. Works very well in my experience.
https://play.google.com/store/apps/details?id=com.tesco.callingcard
for calling the states I suggest you install the tesco international calling card on your phone whilst in the UK. i use it on android, i assume it's also available on ios. you get £2 free credit and the rates are really low. AND you can send texts for free (when your balance is >£1)
https://play.google.com/store/apps/details?id=com.tesco.callingcard&hl=en_GB
don't use it whilst on the continent though.
for a normal phone plan I suggest you use a sim only plan. I have a 4g EE tariff as whilst elsewhere in the EU I can use my minutes and texts for free to call both UK numbers and ANYWHERE else in the EU (BUT not data). I'm not sure if this applies to sim only deals, but if not for £4/day you can get one of their euro passes which gives unlimited calls & texts, plus 100mb/data per day. expensive, but not that bad if you're a heavy user.
http://explore.ee.co.uk/roaming/ee/france
better deals are available for 12 month contracts, but all providers also give monthly rollover contracts.
here is a google doc that is constantly updated with the latest deals. Often you can get cashback by purchasing through sites such as quidco and topcashback
https://docs.google.com/spreadsheets/d/1hFft7bqmSnbVzVlBbp5CFHOnk5i_JyxfzU75Lq4MxHw/edit#gid=17
PS, England and Scotland are in the same country (for now!), the UK.