HMRC can have it both ways and usually attempts to do so. It is not in the brief of the tax man to assuage the tormented breast of the tax payer. Fear and terror are far better weapons in the fight where every one is perceived as a tax evader with criminal tendencies.
The instability in the British tax system is, in my opinion, a grass root which, until it is properly sorted out by the introduction of statute will always discourage investment either corporate or individual. I do not think that any other important economy has a tax structure as complex and so indistinct as Britain's.
It seems to me though that what could have happened here is that HMRC might be attempting to open a new tax folder. Here is what they might be up to.
The pieces of prose within the !(())! are quotations!
It is from this page of the US IRS website.
Foreign Earned Income Exclusion - What is Foreign Earned Income
!((Source of Earned Income
The source of your earned income is the place where you perform the services for which you received the income. Foreign earned income is income you receive for performing personal services in a foreign country. Where or how you are paid has no effect on the source of the income. For example, income you receive for work done in France is income from a foreign source even if the income is paid directly to your bank account in the United States and your employer is located in New York City.
If you receive a specific amount for work done in the United States, you must report that amount as U.S. source income. If you cannot determine how much is for work done in the United States, or for work done partly in the United States and partly in a foreign country, determine the amount of U.S. source income using the method that most correctly shows the proper source of your income. In most cases you can make this determination on a time basis. U.S. source income is the amount that results from multiplying your total pay (including allowances, reimbursements other than for foreign moves, and noncash fringe benefits) by a fraction. The numerator (top number) is the number of days you worked within the United States. The denominator (bottom number) is the total number of days of work for which you were paid.
Example:
You are a U.S. citizen, a bona fide resident of Country A, and working as a mining engineer. Your salary is $76,800 per year. You also receive a $6,000 cost of living allowance, and a $6,000 education allowance. Your employment contract did not indicate that you were entitled to these allowances only while outside the United States.
Your total income is $88,800. You work a 5-day week, Monday through Friday. After subtracting your vacation, you have a total of 240 workdays in the year. You worked in the United States during the year for 6 weeks (30 workdays). The following shows how to figure the part for work done in the United States during the year. Number of days worked in the United States during the year (30) ÷ Number of days of work during the year for which payment was made (240) × Total income ($88,800) = $11,100.
Your U.S. source earned income is $11,100.))!
The point of all of that of course is that it enables a broad global sweep of income taxation while at the same time allowing a calculation to be made as to any applicable with holding tax proportions.
There have been calls from elements within political parties for Britain to move to a taxation system based on citizenship as well as residence. This would probably sit well with the public who would regard having to pay UK tax as a fair trade for a visit from a British embassy official when you were banged up in a Turkish jail for smuggling Greek birds to Albania for prostitution, or any other amusing activity which falls foul of the political police.
Nightstop:
That'll be quite true so long as the guys do nothing to break the 90 day /183 averaged over 4 year 'rule' and thus become resident in the UK. If I lived in Spain there'd be no chance of that happening and anyway you'd still get credit under the double treaty. Mind you, Spain operates a very friendly ex pat working locally based tax schedule on foreign sourced income. It's also true in the case of British residents who leave the country for at least one full tax year under a full time contract of employment.
It's all conjecture but it is hypothesis brought on by the action of the controlling authority and therein lies the problem and the confusion.