Cycle to Work scheme

Hi folks.
Pondering getting a bike on CTW through work (on the Evans scheme) next month. 20km each way from Essex to central London... the distance shouldn't be a problem but the potholed roads and the crazy London drivers might be. I've been biffing about on a Scott Sportster hybrid for a while and clearly something lighter and faster (to say nothing of prettier) is going to be in order.
I'm sure it gets asked on a daily basis but I'd be interested in any recommendations. I'm a bit lardy, 5'9" with 31" leg so think I'll be looking at 53/54cm frames: probably alu with carbon fork. I have a bit of a stiff back that exercise should help, but is it worth going for a full race-type bike? Or one of the ones that are slightly more comfortable (e.g. Cannondale CAAD8 vs Synapse). Or even something like a CAADX to cope with the roads perhaps - although to be honest I'm not sure that'd be much different to the Scott.
Also - how do I convince the Mrs that I need another bike?
Pondering getting a bike on CTW through work (on the Evans scheme) next month. 20km each way from Essex to central London... the distance shouldn't be a problem but the potholed roads and the crazy London drivers might be. I've been biffing about on a Scott Sportster hybrid for a while and clearly something lighter and faster (to say nothing of prettier) is going to be in order.
I'm sure it gets asked on a daily basis but I'd be interested in any recommendations. I'm a bit lardy, 5'9" with 31" leg so think I'll be looking at 53/54cm frames: probably alu with carbon fork. I have a bit of a stiff back that exercise should help, but is it worth going for a full race-type bike? Or one of the ones that are slightly more comfortable (e.g. Cannondale CAAD8 vs Synapse). Or even something like a CAADX to cope with the roads perhaps - although to be honest I'm not sure that'd be much different to the Scott.
Also - how do I convince the Mrs that I need another bike?

Scott Sportster P45 2008 | Cannondale CAAD8 Tiagra 2012
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Posts
A road bike may have a more aggressive geometry which may affect your back. It may not have mudguard or pannier rack attachments. In terms of speed, the aggressive road bike position and drop bars may put you in a more aerodynamic, however if your current hybrid is a road bike style hybrid with road tyres and groupset you may not notice much difference. Also, what's your budget?
Best thing to do would be to try out a few road bikes to find out if you like the ride they offer
How about a cyclo cross bike? Sounds like the perfect tool for the job you describe, and loads of people on here would recommend them. Slightly more relaxed geometry than a road bike, can fit guards etc, and much more bombproof. I've just picked one up from Ebay in great condition for a knock down price, and would recommend that route rather than CTW work to be honest.
A touring bike best fits your need so go for a touring bike instead of a proper racing bike. heres one from evans under £1000:
http://www.evanscycles.com/products/jam ... e-ec031786
Pros:
Better handling, more maneuverability (including passing curbs, park areas without pavement, etc);
When needed, attaching fenders, lights, etc is much easier;
More comfortable position;
Cons:
Slightly lower performance;
Anyone who thinks a road bike is too delicate for commuting honestly doesn't know much about road bikes. The Gran Fondo is tough - the wheels (Campag Khamsin) are tough. The frame takes Crud Road Racer mudguards and they are sound enough that I leave them on all year round. The narrow handlebars are a huge benefit in traffic compared to the flat bars on my MTB. Comfort is fine - if you are uncomfortable on a bike, it is probably because it doesn't fit rather than that it is the wrong sort of bike.
On the other hand, during the depths of winter I do use my old Dawes tourer (mainly because the componentry is much cheaper - an old bike thing rather than a bike type thing) - and last week, both rims on my handbuilt 36 hole wheels were wrecked on one pothole.
So, if you want to worry about a bike not being tough enough for the commute, get an MTB........