Many builders like two to one epoxies for their ease of mixing ratios. There was an independent test done on some brands and RAKA came out on top and it's an inexpensive 2-1 ratio epoxy. Since you're in England, you;ll have to shop around for your brands or talk to other builders in your area.

Epoxy has flexibility and polyester doesn't. That's what makes it a good glue and coating for wood. I once had a puddle of polyester that hardened on my benchÊthat was about 3 inches in diameter. I pulled if off and accidently dropped it on the floor. It shattered into pieces. An epoxy puddle can be bent and will not crack apart.