Hockeyrabbit
Other than the table issue, how are you measuring your cuts? Are you using the grid on the mat, or are you using a two ruler method?
I had always used the grid on the mat to line up and measure my fabric then placed the ruler to cut, and for repeats I would just slide my ruler to the left and keep cutting still using the grids on the mat.
Recently I purchased Sally Collins book "Mastering Precision Piecing" and along with some sewing techniques that I now employ, I also switched to the two ruler cutting method she recommends.
I like doing small piece blocks and with these precision is necessary down to the 1/16". Prior to reading Sally Collins I struggled and had to "fudge" a lot. Not any more.
Get her book, and video. It's all about precision, precision, precision. I call it the "piecing primer".
BTW - I'm using a plastic Beba mat placed on a formica table top. It's not an issue.
Sue