This question is about refurbishing eaves to make them somewhat insulated, and specifically what treatment is best for the transition from felt/membrane to gutter.

I have pretty standard 1960s ventilated roof on cavity wall, with wall plate on inner leaf. The tiles are big (concrete) pantiles, and there is a bituminous felt underneath. The rafters are extended to give an overhang of 200mm.

As bought:
http://wookware.org/house/retrofit/drawings/eaves-before.pdf
After insulation:
http://wookware.org/house/retrofit/drawings/eaves-after.pdf

I took the bottom 3 rows of tiles off to insulate the wallplate/skeilings. The bituminuos underlay was knackered at the bottom edge where it 's been exposed to light, hanging over into the gutter, so I replaced it with a breathable membrane. That explicitly says it shouldn't extend down into the gutter, and you should use a plastic edge tray for the last bit.

The current design has flat tiles at the roof edge, to provide a base for cement to block the gaps at the end of the pantiles. http://wookware.org/pics/house/eaves/tiles1.jpeg

Plastic combs are a more modern and convenient way to deal with the gap under pantiles and seem to work fine. Is there any good reason not to remove the flat tiles, save a lot of time mixing loads of cement to fill them in, and just put a bird comb in instead?

Now whilst looking I discovered that you can buy a 4-in-1 device, which has a membrane support tray at the back, comb on the top, 10mm continuous eaves vent , and edge drip-tray all in one:
https://www.virtualplastics.co.uk/collections/eaves-protectors/products/vented-eaves-protector-support-tray-with-comb-protection-roof-felt-protection

Anyone used these? It seems like a good idea but perhaps I am missing some disadvantage? As you can see There is a tendency to pooling just behind the bargeboard with the current design and a support tray will probably help with that. The comb has the major advantage over cement that you can still remove/replace the tiles easily. At the moment the eaves venting is just by infiltration - there are no vents in the soffit. I carefully left a gap just behind the bargeboard so that holes could be put in (you can see in 'eaves-after' PDF above, but with this vent over the top of the bargeboard I probably don't need any. It's only 10mm so isn't a huge amount of ventilation, but more than before.

The alternative is a separate drip-edge and comb (which screwfix have): https://www.screwfix.com/p/felt-support-tray-1-5m-5-pack/36622

You are a hero! Only another few million do do now!

I love over fascia ventilators, the combi one seems good. I often needed thin ply under my sarking felt to direct water into gutter and stop it sagging

If dag 1 is right then I think they have over notched the main rafters,

I would like to see max pos insulation over the wall plate, even chamfering it a bit between rafters to fir more in, leave 25mm ventilation gap, would prefer sheet insulation vertically up inside skin from top of cavity to top of plate rather than the horizontal piece you have got.

I don’t much like or see the point of the plain tiles, did they put sand and cement infill on them to stop birds first tome round? With bird guard you could miss them out

Re not lapping membrane into gutter, I always laid it so nothing could get between gutter and fascia, ie hung down 25mm into gutter.

I take a more relaxed approach. I have little birdies nesting in my eaves and have noticed a new colony of tree bumble bees in the barn roof. They don't seem to cause any damage or prevent anything from breathing. I don't use the plastic things that keep them out as I quite like to have them.

The birdies do wake me up in the morning at 04:30. How do they know it is about to get light? I get on with stuff from 05:30 and get a lot done during the day.