Possible blown head gasket on MK1 Eunos Roadster 1.6L

Hoping someone can help.
I own a 1992 Mk1 Eunos Roadster 1.6L special edition (first registered in UK in 1998). I have owned and enjoyed this for nearly 20 years now with little or no issues

I live between Newton Abbot and Torquay in Devon (TQ12 5LT). I have been told by the local Halfords garage that the head gasket may have gone on the car – as it has been misfiring and there appears to be water getting on the plugs.

Can anyone recommend someone who could have a look at the car and if required carry out the necessary repairs?