All depends on where you are, accent, how much it annoys you and how the stress falls in the name (would the last syllables be emphasised?) I think I like Kate or Bethan the best from your girls names, and definitely Laurence.
Ruth Megan Vivienne Ellen/Helen Eve Faith Iris Juliet Claire Tamsin
My DD has an 'a' ending name and an 'er' occupational surname and it's been I problem to her. In fact it never crossed my mind until you mentioned it! She's lived with it for 13 years so I assume she's ok with it.
Trying to think of famous examples..
Lana Turner Ava Gardner Jessica Fletcher (!) Sarah Jessica Parker
My first and last (married name) both begin with the same letter and both end in an "uh" sound and it sounds ridiculous when you say them both together. So I'm guessing that you just have to work out whether it sounds wrong to you or not.
I'm having major collywobbles about this whole 'pick a name' malarkey. DH has made his choices, but I'm kind of stunned into inaction. It seems like such a big decision, and that I should be making my choices based on something more significant than 'I thought it was a nice name'.
Is there anything in your life that you are really into -- music, the books of some author, some book you read, some painter's work, some place you would love to visit or some place you loved when you visited? If there is anything with good associations that might lead to a name, maybe focus on that. It's nice to feel the name you choose is in some way connected to you and your life.
My niece has a name ending in 'a' and surname ending 'er' that doesn't bother me at all.
However, my first name ends with the same sound as my middle name starts. It has bugged me since I can remember and makes it sound like a mouthful. I don't think my parents ever said my name out loud before I was registered, or They didnt care