This too little info.
For example my gf has 4% deducted from her salary as gross salary sacriface and the company adds 12% into her pension fund so basically 16% of her salary which is very generous since she loses only about 3% of her take home pay.
In theory this will give her a very good pension and not far behind final salary scheme (lesser ones)
On the other hand her Mother is in a final salary scheme and she gets 49/80ths of her final years salary which will mean a very generous pension of around £40k per annum plus an initial lump sum of £120k.
However I know many other people with less generous final salary schemes.
Assuming the final salary scheme still exists when you get there, it's easy to work out what that is worth. Then easier enough to figure out hoiw much of your extra £5000 per annum you would need to put into a pension scheme to match the same final salary payment.
You might find that it takes all of the £5,000 or even more depending how generous your final salary schem is.
In my gf's mother's case I am nopt sure you could have paid enough of your salary into a pension to return around 2/3rds of your salary in a private pension.