First I would check when you are entitled to OAP. My wife and I were born in 1955 and were not entitled to OAP until age 67.
My wife didn't defer her OAP and was taking SS before her OAP was due. She too had applied through the FBU in London and the month she started receiving OAP her SS was reduced due to WEP. So, I can't answer the question about the effect of delaying taking OAP but I suspect it would be on the due date. That would make sense to me because I believe delaying OAP doesn't increase it except by the normal COLA amounts and when you apply for OAP the back years are then paid through increased payments or possible as a lump sum. (This happens sometimes when folks don't respond to the letter from DWP telling them they are eligible to apply for OAP)
I don't believe withdrawals from a defined contribution plan affect WEP, in fact I can't think of any way they could logically apply that. I believe only DB pensions and annuities from employment are considered.
Lastly I would look at how much the company pensions would affect WEP because WEP only applies for a portion of your SS, up to the 1st bend point. If the OAP exceeds the first bend point, currently at $1,024/month then delaying the private pensions beyond the OAP age will not effect WEP at all. (SS reduced at most by $512/month)
e.g. Full OAP is currently £185.15/week or approx $1,010/calendar month at today's exchange rate which pretty well fills up the maximum WEP bucket so more pensions will not lower SS by much more.
https://www.ssa.gov/oact/cola/piaformula.html#:~:text=For%202022%20these%20portions%20are,of%20the%202022%20PIA%20formula.
Note also that once you have more than 20 years of SS contributions the amount of WEP goes down until it is zero at 30 years.