The British Pound is always displayed with no padding between the £ and the figure
http://www.royalmint.com/discover/uk-coins/circulation-coin-mintage-figures
Therefore, the following code needs to be amended:
"GBP" => array("name" => __("Pound Sterling", "gravityforms"), "symbol_left" => '£', "symbol_right" => "", "symbol_padding" => " ", "thousand_separator" => ',', "decimal_separator" => '.', "decimals" => 2),
to:
"symbol_padding" => ""