Holiday pay help please

[Davlers]

Hello all I hope someone can clear up some confusion about my holiday pay and I apologize if it's been done before .
So I've worked for the same company since 1990 I started in September. As I understand things I was in the old system, I needed to work until April of the next year accruing holiday days as I went. Come April I now had x number of holiday days earned to use the following financial year, so when April came around again I had a full years entitlement at the time 23 days and it's been the same way since although management put in place a bonus system for every 5 years service you gained another holiday day. So as it stands now I currently get 27 days plus bank holidays.
I can take these days in a block or single or even half a day when needed. For a single day I get 8 + 1 hours at time and a half.
The thing is when I take a week off to go away I get 5 days holiday pay which is over £100 less than my take home pay for a normal week as I work from 7 to 5 ( which equates to 8 + 1.5 at time and a half) and recieve a £6 per day chargehand bonus. I have since learned that I should get a full weeks pay , an average of 52 weeks pay.
Is this correct ? Because as I have been there for so long I have been down £100 per holiday week for a long long time (4 weeks per year for let's say 20 years to be sure ) £8000 minimum
Am I misinformed or got the wrong end of the stick.
I'm in the UK
Thank you very much.

Your holiday pay should include any regular overtime and bonus. So yes, you should be getting a full weeks pay. However, you cannot claim for the full 20 years. You can only claim underpaid holiday pay for a maximum of two years. Depending on the pattern of your holidays, you may not be able to claim for the full two years.

So you didn’t take any holiday in that first year? That seems odd in itself.

In addition, I think your initial calculation is incorrect.

You started in September, with a holiday year running from April (so I assume 1/4 to 31/3? ) in this part year you were accruing holiday for use on that period, and when it rolled around to April, you should then have had a full year’s entitlement for the first full year you worked (1/4 to 31/3)

although, after 20 years, the chances are that there are no remaining records to prove this.

I think it was only fairly recently (2013?) that regular overtime was legally required to be used to calculate holiday entitlement. My DH used to work 40 hrs double up his wages with 20 hrs overtime (hgv driver) so only got half his usual pay if he took a week off prior to this ruling.

When I first started way back we 100% earned our holidays a year in hand. None from sept 1990 to Apr 1991 then around 14 days ( earned from sept 1990 to Apr 1991) to use from Apr 1991 to Apr 1992, then we got the full entitlement of 23 days to use from Apr 1992 to Apr 1993 and so on.
It definitely the case as us old timers tell the new lads how hard that first year was with no holiday days. The new starters can use holidays right away. I believe the law changed sometime in the distant past to enable this. Thank you for all your replies.