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TheDeathOCuHullainn The entire archipelago is the "British Isles", but I agree the formal title is "the United Kingdom of Great Britain and Northern Ireland".
I do wonder what would happen if all the secessionists had their way and broke up the United Kingdom, as they want but are reluctant to admit.
The Republic of Ireland is successful in her own right, and would gain the Harland & Wolff shipyard that has just gained an important Royal Naval contract.
Scotland would trade for a few decades on oil and natural gas, and the employment these create, but those are limited and unlikely to last more than a few decades. It may be able to revive or at least protect ship-building. So-called "renewable energy" does provide manufacturing and installation employment but very little operational work. Scotland would need come to some arrangement with England over the RN and RAF bases, and defence-research facilities, in Scotland; and which also provide a lot of employment. This might be as fellow NATO members, or via some non-EU, European equivalent.
Wales still has limited steel-making and I believe one surviving coal-mine but not much other industry apart from farming and tourism.
What they do not air is how they will relate to the rest of the world: the UK is a member of or signatory to, a huge number of international bodies and treaties: UN, NATO, ISO, MarPol, intelligence- and police- co-operations, scientific projects, etc..
Nor do they air how with the loss of admittedly-modest money from Whitehall, they will fund all their own public services: currency and national finances, health & welfare, hospitals, education, transport (vehicle registration and taxing, roads, railways, airports, harbours, public-transport fares subsidies), the emergency services, defence and security, judiciary, prisons and probationary services; and so on.
They may be able to attract the so-called "service industries" - tourism (seasonal, unsociable hours, low pay), taxi-driving, and tapping away on computers in cheaply-built offices. The last employs comparatively few people for the turnover, much of it is foreign-owned and AI may mean far fewer humans in such work.
A united Ireland could survive, even thrive, as an extension of the present Republic - even if you don't care about those citizens who do not want that - but I doubt the other two would.
Southern Scotland would probably manage, but generally the country, geographically related to Scandinavia, would likely see a Scandinavian scale of expense for residents and businesses. Once the oil runs out the enormous area North of the Glasgow - Edinburgh band would likely fade, economically. Its rail links, presently part of the fully-national system, may become too uneconomical North of those two cities and perhaps Dundee. The motorways, perhaps 200 miles of them, would be very expensive for Scotland alone to keep up to scratch. Distance alone would make the country unattractive for industrial investors apart from the "renewable energy" trade, which itself will face an uncertain future with the depletion of its necessary petroleum-derivatives and scarce metals sources.
Wales risks being worse off still. Most industry is around Swansea and Cardiff. The main income in the North is tourism, in an area that is also reputedly the least friendly to the English (while taking their money). It would likely also lose most of its railways, leaving that linking London and Bristol to those two South Wales cities, and along the North coast to Holyhead. It may be able to maintain the M4, which ends just West of Swansea, and create a cost-sharing agreement with England to look after the Severn bridges; but not pay for much else of its very extensive road network. The rest of Wales is primarily agricultural; a very shaky trade even though most people still insist on eating.
