Sunday needs to have earlier services - in Reading the first fast train to London is not till 09:38 and then there is another hour gap after that - previously a semi-fast train at 08:20 had run and always was quite busy when I took it. Also, another example is the first Oxford to Reading train not being until 10:16 - that is crazily late. I think for the most part Sunday services don't necessarily need to change for the afternoon and evening but we need earlier trains in the morning.
Also, my other complaint would be Saturday evening trains - take London to Reading as an example again - Monday to Friday and Sunday there is an almost 24-hour service as there is a train at half 1, half 3 and then 5am all in the morning. On a Saturday evening - a popular evening to go out - the last Reading train is at 23:45 and the next train is not until 07:17 on Sunday morning. I have once been stranded in London due to tube delays on the circle and h&c meaning i missed that last train at Paddington - fortunately I have family in London but others may not be as lucky.