So, you want to study specifically the Christian situation for online dating in the United Kingdom. But in any country with Internet we can have Christians who are only cultural, who are dating; and there are ones being guided by God.
And the results and stories of the cultural ones can have statistics very different than what you could get from God-guided people.
So, in order to see who is giving you your answers, you could ask for a brief story telling how a couple came together, and what they say worked.
I would say statistics alone can't tell you what you might want to learn.
In my case, while I was less mature and experienced, I met people both in person and on the Net. The results were similar > things worked out according to my character and level of maturity. At first, I was just falling for people I didn't even get to know and getting into problems, because I was not mature and wise, even though I did seek to submit at all times to God.
As I grew, I did better in person and on the Net. Then, in my case, I met my lady friend without trying to find her. It worked out in church and then more and more elsewhere. And our character, I can see, has had a lot to do with if and how well we have connected and developed with each other.
So, statistics and general questions might not tell you what my individual experience can. Possibly, if you have not, you should get to know some people and hear their stories, and in your survey include a request for each person's testimony about how things actually happened for online and personal dating.
In my case, by the way, I never was aiming at getting married, and I made this clear with Net friends. So, you might ask if someone intended to find a date or mate, on the Net or in person.
And, as one seeking to be guided by God, I tried to not steer what God would do with me. I think this is how God has had me do this, while He could have others making specific goals and requests. What has being guided by God involved, then? How someone approaches this might need to be evaluated, along with roles of the Net and services and in-person relating.