Soil pipe into ground level gully

I currently have a ground level open gully that is taking waste water from the kitchen to the main foul water drainage system. The gully feeds to a swept bend in the household foul water drain - with an inspection cover over the joint. I'm 99% certain there is a P-trap (or simillar) between the open gully and the swept bend. I want to add an upstairs toilet and was wondering if I can feed the soil stack into this gully drain, capping it off so it is no longer open (and joining the kitchen waste pipe into the soil stack). Is that :
a) sensible
b) notifiable under BCO? I'm not changing ANY sub-terrain drainage
c) compatible with the current gully p-trap? Are soil pipes able to empty via a p-trap or must they go direct to the swept bend?

Any advice greatly appreciated.

 

Thanks KIAB. The trap thing will be a pain in the neck. There is a 4 inch thick concrete pathway on top of it (i.e. the gully goes into 4 inch thick path and the pipe then runs under this path the to the swept joint) so I'd either have to break through the concrete that and dig down to replace the trap with a resting bend, or dig down beside the path and then dig under the path to replace the trap with a bend. I guess I'd better check if there really is a trap there or not before I decide on my plan of action. There should be trap there but not everything on this house has been done properly.

 

It does indeed feed into the foul sewer and not a soakaway. Further inspection confirms there is a trap in the open gully but not an inspection chamber over the joint into the main foul sewer (the inspection chamber I previously mentioned actually services a downstairs toilet). So I need to at the very least remove the trap and fit a rest bend. But would I need to retrospectively add an inspection hatch to meet regs? I have considered not going for regs (but fitting the rest bend in a compliant manner) but have concerns for when I come to sell.

 

Thanks all. Spoke to BCO who confirmed your statements. He suggested I include a rodding point in the soil stack. Now I just need to decide whether or not to actually register or just do it and hope to get away with it when we eventually sell.

 

Normally I'd keep quiet about it but got caught out when we came to sell our previous house. The property form asks if you've made any changes and writing "added an ensuite" would, I imagine, attract requests for buildings regs documentation from the buyer's solicitor