Due to the one carry on rule in the UK, if I put my purse into my carry-on and go thru security..may I take it out once I clear all security points and take it onboard with me along with my carry on???

Thank you.

yes - the 1-bag rule is only for going through security. After screening, you can do what you want w/ the handbag/carry-on.

we were in Gatwick several times in dec and jan, and my wife was able to combine several bags into one to get through security. However, I think to play it safe she kept them all in one bag until we boarded.

There's no "play it safe" here.

The business model of Gatwick is all about maximising retail sales. All shops are after security, so the system is perfectly clear than you can add as many bags as you like once you've been through security. Indeed, Gatwick strongly encourages you to.

After security, it's up to the airline how many pieces you can bring onboard. Some low-cost airlines still only allow you one piece to get onboard.