Hi @sam093376 ,
Thank you for your post.
There is a collection option for Royal Mail with Simple Delivery. Please see the below

With regards to the package size. If you use the recommended parcel size and your item exceeds the maximum size and weight of the label, you won’t be charged any additional costs. Just go ahead and use the Simple Delivery postage label. The courier will accept your package providing it remains within the maximum weight and dimensions for the service.
Thank you,
Kat
I am currently out of the office and will return on the 15th of September. Please expect a delay in my reply