Is this a good first time mrathon training schedule?

I'm currently training for my first marathon (Sunderland, April 28th). Until recently I was just a recreational runner: 3 or 4 days a week I'd run at an easy pace for 30-60 minutes. Over the last couple of weeks I've started doing 3 mile tempo runs and slowly increasing my long runs (my last was 9 miles). My new schedule looks like this:

Sun- 6 miles at easy pace
Mon- 3 mile tempo
Tue- Rest
Wed- Long run
Thu- 3 mile tempo
Fri- Rest
Sat- Rest

Running and resting on these days best fits my schedule so I won't be changing that. My idea is to keep the other 3 runs the same each week and increase my long runs each week. I want to get up to a run of around 30 miles before the marathon (I know a lot of programs peek at about 20 miles but i would rather know I can manage beyond the race distance).

Is this a feasible training program?

Generally your second longest run should be half the distance of your longest run, so if you want to do a 30M LSR you need to build up to a 15M medium long run.  However, I can't say I'd advise a low-mileage first-time marathoner to go beyond 22M as their longest run.  The injury risk is just far too high.  I also don't think it's a good idea to do a tempo run and your long run on consecutive days.  Both count as a quality session and should be separated by a rest day or short easy run.