While you were working abroad, you were definitively non-UK resident under the automatic overseas tests(see here
and from page 9 here
). Now, as you spend more than 45 days in the UK in a tax year you do not meet any of the automatic overseas tests not do you meet any of the automatic UK tests so its necessary to refer to the sufficient UK ties test to determine your UK tax residence status for any one tax year.
As you were non-UK resident in the three tax years prior to your retirement, you will be treated as an "arriver" for the purposes of the statutory residence test. You should refer to the table under "Arrivers" here
and to paragraphs 1.42 to 1.45 on pages 28 and 29 here
If you spent 182 days in the UK in any one tax year, you could have no more than 2 UK ties as defined under the "Arrivers" heading here
. That would reduce to 1 tie if you were UK tax resident in one or more of three preceding tax years or you spent 90 days or more in the UK in either of the previous two tax years. The tie that you have is your UK property and the one that you may acquire is that you may spend more than 90 days in the UK in a single tax year. So, spending 182 days in the UK in a tax year for the first time since 1973 may make you resident in the UK for that tax year if you spent 90 days or more in the UK in either of the previous two tax years.
You can find the tax rates and personal allowances for the UK for 2015/16 here
. How much UK tax you would pay would be dependent on the type of income you have and whether any foreign tax is paid on it. Foreign pensions are given a discount of 10% so you would pay tax on 90% of one of those if you were UK tax resident. Some government service pensions might not be liable to UK tax depending on the tax treaty between the UK and the country from which the pension is derived.
From 6 April 2015, non-UK residents became liable to Capital Gains Tax in the UK on gains they make from that date on the disposal of UK residential property. Most will choose to pay only on any increase in value from 5 April 2015 but there are other options to individuals which may be more beneficial depending on their situations. You can read about this change in the law here
. CGT is charged at 18% or 28% or a combination of the two rates depending on the level of the taxpayer's income in the tax year a gain is made.
I hope this helps but let me know if you have any further questions.