Your right about that. Prior to WW2 Irish Linen was a huge market. I think the term "Irish Lenin" is still synonyms with quality linen. Belfast in its past had been called Linenopolis.It was quite surprising how much was sub contract in the building of Titanic ship and others too at H&W. Ireland does not have raw materials as mainland England & Scotland had. There is a book by Andrew PB Lound. RMS TITANIC MADE IN THE MIDLANDS. Quite an eye open what was built in England and then ship to Belfast. H&W may of had the machine shops but not the raw materials as were imported.
That quoted figure of 14000-15000 working on the two ships Olympic & Titanic is wrong. That is the total work force of H&W at the time. They had six other slipways turning out ships. Total figure working on the Olympic & Titanic is nearer to 3000-4000. Titanic was built on slipway No 3. Olympic No 2. I have been there. It may surprise you to know that shipbuilding in Belfast was not the largest in employment at the time! Textile industrial was the largest employment!