The forecast is for 8/8th blue tomorrow, so IMC shouldn't be an issue.
The majority of IFR Exeter traffic comes from the BCN direction or from the south via BHD, so there should be relatively little coming at you from the East. If you talk to Exeter Approach they will know of anything expected or in the area.
Make sure you route around D011 (Okehampton) as it is often active at the w/end. It's easy to do by following the A30 until you get to Okehampton.
It's a lovely trip on a nice day, especially when you can see the sea on both sides and the land narrowing towards Cornwall. Enjoy!