No, as a Private seller Simple Delivery is now mandatory . There is no more opting out.
However, there is currently an issue that Simple Delivery not offering Custom Postage to oversize items, lightweight items and those under £10, these are all exempt from Simple Delivery.
There is a workaround.
From the link below Go To Solution and follow the advice in Rick's answer to list your item.
https://community.ebay.co.uk/t5/Seller-Central/how-do-you-list-anything-bigger-than-61cm/m-p/7882638...
@dubbin901
