Recommended approach on my training going forward

My question is my training going forward.

I’ve 36, 5’8" and about 155lbs. Live in UK.

Running is basically my form of commuting. I run 5 days a week Monday to Friday and run is 5km direct each way. Mostly downhill on way to work with small rise at end (about 160 ft elevation) and slight incline on way home but only about 300 feet of elevation overall.

Once a week normally on a Thursday morning on my run to work I do a longer run of 10 to 12km and also sometimes add a couple KMs when time permits to my other runs to and from work. I don’t do any running on a weekend. I’ve been doing this for about a year or so after building up over a period of time and body is used to it.

I also use a stryd running power meter so can guage effort and gather TSS. Most runs are an easy effort although I have started doing a tempo run on a Tuesday and Thursday longer run is more intervel based. Although I have no specific running goals, it is a form of commuting (avoids hassle of cycling in rush hour) plus it’s great destresser for me with work. I can run just over 19 minute 5km so I’m an ok runner.

Longer term tempted to enter a few races over 5km and 10km with even longer term goal (few years once my kids are older) of doing triathlons with goal of eventually completing an ironman.

On weekends I do two rides on Saturday and Sunday. I do these even in winter regardless of weather unless it is icy.

The bike rides, Saturday ride is a tempo group ride in a chain gang for 45km then race to top of a climb which is a 5 minute effort. Regroup then tempo again for 10km with a sprint finish. So like a race simulation with some structure over same route.

Sunday ride is also a group ride, more social but with a few efforts and normally 70km to 90km ride.

As I say I have no specific running goals, feel it gives me a good fitness base and I know that can’t replace bike specific training but has helped and is an activity I enjoy for commuting as feel it gives me more bang for my buck.

My cycling goals are I have a long sportive ride in June 2019 which is a coast to coast ride in a day across England, 250km with a decent amount of elevation which I want to complete in a good time.

I also have a fornightly TT league but on standard road bikes which is a league of 10 races which runs from May to September over 16kms.

My goals is to improve my performance in these while also being competitive on my Saturday group ride, especially improving my five minute power for the climb.

Now I’m just considering best plan as I have started low volume sweet spot base accounting for running I do and outdoor rides, the longer ride on the plan will normally be replaced with my outdoor ride unless it is too icy to go out.

Apologies for long post but thought I’d give as much information as possible, my question is if I select low volume would it be ok to add one or two sessions to it if I have time/energy? If so what sort workouts would you do? Also going forward what would you recommend for a the build and speciality phases?

Appreciate any advice and input.