I have never ran in Swanage so cannot advise specifically but if you don't mind some undulating off roadish runs then the coastal paths of dorset have been among my favourite holiday runs. It is also pretty easy to get the coastal buses so it stops you having to do an out and back,
Just remember to pop your clothes off when you get to Studland, you do not want to upset the nudists,
1) Do a calorie lifestyle calculation (basically those average daily allowances are way lower for many people). Spend a couple of weeks tracking your calorie intake and work out the areas where you break the bank and try to adjust.
2) Think about ditching the gym. I know they work for many but for me the benefit per hour was nowhere near just lacing up, stepping out and running.
3) Educate yourself on your distance, time and pace. For me that meant a gps watch but does not necessarily have to be that way. Sometimes I just was not aware I was going to fast or to slow.
I am in a similar position. I have chopped up a c25k program and am using the second half of it. I am doing the run sections at my old training pace mixed with reducing walk sections.
I am hoping this gets me back to doing 5k at somewhere near my old pace. I also have some timber to shed but am just hoping that takes care of itself as the training increases.
No idea if this is sensible but previously I was just going out and jogging 5-7k struggling through and not really having any improvement on pace. I found that training plans cover people that cannot run at all or people that can and want to get better, but I was finding that I was somewhere in between.