Yes they do.
Some countries have a reciprocal health care agreement with the UK (e.g. the countries in the EU, Switzerland, Australia and New Zealand). UK residents are entitled to necessary medical treatment on a temporary visit to these countries, either free of charge or at a reduced cost by using the European Health Insurance Card (EHIC) which you can apply for at your local post office or by calling 0845 606 2030 or online at www.dh.gov.uk/travellers
However, goodtogoinsurance.com covers many crucial costs which are not covered by any reciprocal health agreements. For example the cost of repatriation, additional accommodation costs or the cost of a relative or friend to stay behind, or travel from UK, to accompany you home if you are ill. Moreover, a substantial contribution from the patient towards treatment cost is often required under reciprocal agreements and prescriptions and emergency dental treatment are often excluded too.
If a customer does have an EHIC card and it results in a reduction in the medical costs that GTG have to pay, GTG will waive the excess on their claim. So it's worthwhile.