demo, MySQL - rextester

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#MySQL 5.7.12
#please drop objects you've created at the end of the script 
#or check for their existance before creating
#'\\' is a delimiter

DROP TABLE IF EXISTS yourTable;
CREATE TABLE yourTable (date varchar(10), time varchar(20));
INSERT INTO yourTable (date, time)
VALUES
    ('27/04/2017', '11:30'),
    ('01/05/2017', '20u'),
    ('02/05/2017', '20u30'),
    ('03/05/2017', '21h');

SELECT
    CONCAT(RIGHT(date, 4), '-', SUBSTRING(date, 4, 2), '-', LEFT(date, 2)) AS date,
    CASE WHEN time REGEXP '.*[uh]$'
         THEN CONCAT(LEFT(time, CHAR_LENGTH(time) - 1), ':00:00')
         ELSE CONCAT(REPLACE(REPLACE(time, 'h', ':'), 'u', ':'), ':00') END AS time
FROM yourTable;

SELECT
    date, time, UNIX_TIMESTAMP(CONCAT(date, ' ', time)) AS ts
FROM
(
    SELECT
        CONCAT(RIGHT(date, 4), '-', SUBSTRING(date, 4, 2), '-', LEFT(date, 2)) AS date,
        CASE WHEN time REGEXP '.*[uh]$'
             THEN CONCAT(LEFT(time, CHAR_LENGTH(time) - 1), ':00:00')
             ELSE CONCAT(REPLACE(REPLACE(time, 'h', ':'), 'u', ':'), ':00') END AS time
    FROM yourTable
) t;


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