That's an hell of a stab!
This is indeed an Helian:
from a well known site:
'The car started life as a Riley RMA saloon, these cars are prone to body rusting as the rear window fitted in a fabric roof leaked badly and the rear body suffered. In the late 1970's this Riley was subject to a complete overhaul of the chassis and mechanics and a new body fitted as you see it today.
The body conversion was commissioned, designed and built in Angelsey, North Wales, by two boat builders, originally built as a prototype small production run to utilize the abundance of rotten RMA's, this was the only car ever produced. No ordinary special this car was completed to a very high standard. The car emerged as the "Helian Special" and was bought by an art dealer. Several owners have enjoyed the car since including the Editor / Secretary of the Riley Owners Club who enjoyed the car in the 1980's. The car is well known and registered with Riley Owners Club'