UKH

My bike is bottom-of-the-range Decathlon, a sturdy workhouse for an old lady pottering around doing errands. My pottering has developed a bit, I'm doing 20 mile rides or so and would like to do more, and am in top gear on the flat. And even the boris bikes that I use in London have a better freewheel and a smaller bottom gear. Any suggestions - if not for a particular bike, perhaps for a type of bike? Or even some useful vocabulary. I want to be able to go off road a bit, but not on very rough ground.

Gravel bike

Mid or high range decathlon bike they are great! 

Is it a mtn bike or a road bike you currently have?

Do you want to be in a more upright position, and sacrifice weight and speed for comfort? £500 hardtail (front suspension only) is what you're after. 

Do you do the majority of riding on tarmac or well packed gravel trails/forest roads, and don't mind a more hunkered position on drop bars? Gravel bike is what you're after (like a road bike, but higher volume tyres for a bit more comfort)

Got a budget in mind? Makes it easier for people to suggest things. 

Take a look at Cube bikes. They are designed for people like you. (And me, I have one). If you want a cheaper option have a peek at Dawes. Great bikes for a good price and I think they are still made in the UK? Perhaps.

Type of bike. Sounds like you need a hybrid. Good for forestry tracks and also good on roads. 

Agreed. Hybrid is a good idea.

I used my old 25 year old one heading up the estate roads at Blair Atholl recently. It freewheels quicker than a mountain bike, so goes faster on the road, due to narrower tyres, but the tyres are more rugged.

Thank you all this is so helpful.

Hybrid sounds right - roads plus say forestry tracks.

Would happily spend up to £500 I think, but happier to spend less.

Hard to answer the question more upright for comfort vs more hunkered. Probably more uprght.

Googling around a bit I like the look of the Dawes hybrid.

I have a Dawes Hybrid (Mojave I think) whoch I use for exactly as you are describing. Its a very smooth ride and feels solid. I paid around £350 for it but shop around. Enjoy your cycling! 

Another vote for a hybrid. A hardtail MTB will be harder to peddle on the road than a hybrid, and if you're in top gear on the flat on your current bike, (not sure what type of bike it is), you may well find MTB gearing is too low and you'll end up going slower on tarmac than on your current bike (with more effort required to overcome the rolling resistance of the tyres).

If you can, I'd recommend visiting a shop or two and sitting on as many as you can. The key thing is getting a bike that excites you and that you want to ride - it's an emotional purchase as well as just a practical one.

Practically, think about position etc as per above, and also whether you want mudguard and/ or rack mounts, a suspension fork (maybe not for mostly road riding) and, if you're not handy with tools, whether you want a relationship with your local bike shop. 

Enjoy!

^^

This.