Harriet I am so sorry to read about your miscarrige. I cannot even begin to imagine the pain you must feel at the moment.
You ask about IVF clinics. I am not sure if you have had any investigations into the reasons why it has taken you 7 years to conceive but given the time frame (based only on my personal experience) I would be surprised if you were not referred very quickly for investigations.
Please excuse me if I am treading where you have already travelled but the first thing that would happen would be to have your partners sperm checked and then you would be assessed to see if you ovulate and how your "ovarian reserve" is. These are simple tests. They also generally examine you for structural issues such as problems with your uterus using ultrasound. They will also test to see if your "tubes" are open and free....this is done in one of two ways but is a more invasive procedure and needs a day in hospital.
Once they have examined these issues then a choice about what might be the best route to help you enhance your chances of conception are.
For example clomid is a drug to help your ovulate should that be the issue.
In my particular case there was not problem that could be determined using the tests they have currently.
We went on to use IVF (if there is an issue with sperm you can use ICSI - intra cytoplasmic sperm injection where the embryologist aids fertilization) since my husbands sperm are functional (at least outside of me!).
IVF is a gamble - that is something you need to know going in. But you can be assured that you will be guided very well by the fertility specialists as to how successful they think you will be.
The following website is a very good and very accurate source of information. www.hfea.gov.uk/
Look for a clinic that is as good as it can be but keep in mind that you will may have a lot of visits (some short and some long).
I hope that this helps and that I am not just telling you all that you know already.
I wish you every success for the future.