Hey @Jappacake, are you having issues receiving SMS only from this specific contact? He/she would need to make sure to be using the correct dial code for sending an SMS to the UK which is +44. His plan also needs to include international messaging. Another thing to do is to get in touch with your Network Provider (your friend would need to do the same with his/her provider), to make sure you both don't have any blocks or restrictions.
I had a similar problem with hindi and love sms. This is something like templates with text. I did not understand what the problem was, but I was helped to solve it in the service center where phone repair, I know that this is very strange, but I found a solution there. One young man fixed everything:) It is also possible that you have a problem because you are from different countries... I use several applications, they are convenient and I think that there will be no problems with them I can share one convenient and reliable application . Try to do as I do, maybe you will meet kind people in the service like me:)