Moody's Analytics obtains annual and quarterly national accounts data for the U.K. from the ONS; the annual data are the sum over four quarters. For consistency across frequencies we have changed "observed attribute" on the quarterly series to SUMMED. This does not change the values of the series (when viewed at its native frequency), but may affect the output of frequency conversions. 

The series reside in the historical catalog (United Kingdom » National Accounts » Additional Detail » ONS - Detailed - National Accounts » Quarterly | Annual) and are:

• ONSNAABMIA.IGBR  = Gross domestic product, (Mil. Ch. 2015 GBP) - Annual
• ONSNAABMIQ.IGBR  = Gross domestic product, (Mil. Ch. 2015 GBP, SA) - Quarterly
• NACEGDPMPAQ.IGBR = Alias
• GDP$.IGBR        = Alias

Please be aware that:

• To perform a frequency conversion with default settings, use the "frequency" control in View, Basket and Chart modes.
• To override the default settings, write a custom formula using the CONVERT function (see related article). You can, for example, compute a lower frequency that is the final observation, the average over the period, or the sum.
• The "observed attribute" of every series (see related article) is listed in Mnemonic 411.