Job done! Got the rad out as SimonH proposed. Loosening the right tie rod is mandatory, the left can remain in place. Thorugh cleaning round the drain valve where the leak was, got rid of all black paint to expose the metal. Five minute job with the soldering iron, then filling the rad with water and left it upright overnight. No leak! Put the rad back, connected the hoses with a little help from silicone grease on the tubes. All tightened up. Tried to refill coolant through the expansion chamber, would not enter. Solution: putting my mouth to the opening of the chamber, applying pressure by blowing strongly until first air and then collant escaped through the drain valve. Closed the valve, added coolant utill full; then start up with no problems . Watched the temperature gauge rise, heater functioning properly, engine block warming up slowly. Gauge stable at approx 90 degrees Celsius. Tightened all jubilee clips, no leak. Seems a sucsess!
Watchpoint: the rad has sharp corners and is a tight fit under the cowl. When you introduce the rad from below, take care so the upper corner does not make a dent in the cowl from the inside!
