In Excel, numbers, currencies, or daters - they all are really numbers. When you format a cell, you don't change the number you have there, you only change how this number is displayed.

So when you enter 262.78 into cell, and left the format of cell General, there will be number 262.78 stored, and it is displayed as 262.78;
When you format the same cell as number with 4 decimals, the number itself remains 262.78, but it will be displayed as 262.7800;
When you format the same cell as number as integer, the number itself remains 262.78, but it will be displayed as 263;
When you format the same number as currency, the number itself again remains 262.78, but it will be displayed accordingly of the currency format set for OS of your computer, i.e. £262.78 for you, or something like $262.78 for US user, or 262,78 € for many of other European countries;


When you celect a custom format for cell, there is possibility to format the same cell to be displayed as (£262.78) too - and again the number remains same;
You even can format the same cell as date - you get some date from year 1900, plus some hours, minutes and seconds in case you set this format to display the time too - and the real value of cell will be 262.78.

When you concatenate (i.e. use formula containing & operator) some number with any string, then the result is always string!