i'm a mature grad too, and this cycle was my third application to med!
The first twice i took the highly risky strategy of applying to all 4 GEP's, which failed miserably.... This cycle I thought "nevermind money i need to get in" and applied to all 5yr courses - I got 2 offers this year, and am off to HYMS in a few days

You have an excellent academic background, science based, so that is a bonus, and will give you more options.
Most people tend to opt for a mixture of 4yr vs 5yr courses
On a work experience note, I would suggest you try and get some more - most unis who like grads like them to have a good length of experience within a caring role, this can be a wide variety of roles, but usually these take a while to set up, as for the majority of tham you will need to have a CRB check, and these can take a few weeks.
Not a very structured post i know, and it doesn't read well, but I'm so keen to encourage other grads that it all just sort of splurts onto the page :S
If you want to chat more or need any more info, don't hesitate to PM me
Sarah
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