Day rate 'After tax'?

Paid by the hour - 13 hours @ £15/hr = £195 top line .
£195 x 5 days = £975 + 4 nights out @£25/night = £975 +£100 = £1075 top line pay Tax, insurance and pension still have to be deducted from that £975 lets say 25% (This only a guess I really dont know what tax and N.I rates are )=£731 + £100 night out money = £831
If you get a bad week and your hours drop your pay drops a good week and you earn a bit more
You have no control over the amount of money you can earn - cancelled loads , parked up early , boats not sailing - thats the risk you take on hourly pay.

Paid by the day - 5 days @£150 a day take home = £750 + £100 night out money = £850 in the bank each and every week .
If I work 45 hours one week I have £850 in the bank if I work 60 hours the next I have £850 in the bank .
If I can do a sixth day then I have £1000 in the bank . Its the companies job to work out what my top line is they work it out tax and National insurance is "dead money " it had to come out of my pay but its not money I can spend so why does it matter to me - it dosent , the only thing that matters to me is how much I bank each week that I can spend . Top lines are meaning less , hourly rates meaning less .
Yes some weeks I work more hours and the company wins but some weeks I work less hours and I win you have to know the hours you work and where the break point is - where you start losing and the company starts winning . If the company is winning to many times then another £10 a day may be needed to balance the odds thats the risk you take on daily pay .