Honda Accord - pick up a very good 1.8 manual easily with your budget. Older or high mileage 2.0 litre for the same budget.
Electric windows, ABS and air conditioning (combined with heating stops yer windows fogging up on rainy days), decent fuel economy. Nothing ever goes wrong with them, so your maintenance costs will be low.
Prolly get about a V, W or X reg with reasonable milage for £1500 - Depends on condition. For £1500 you can't go wrong.
Alternative might be a Toyota Avensis, but they tend feel worn out and saggy in that price range.
Smaller car, look at Toyota Corolla - very reliable. Comes with reliable electrics and will polly have air con as well.
And you don't want to be turning up to client site in a Micra.
Problem with small cars, is that they can be tiring to drive - engine is normally puny and therefore noisy when on the motorway. Also tend to have less noiseproofing, which contributes to tiredness if you're travelling to client sites.
I've used my Accord (on my 6th one) for regularly travelling to clients 4-5 hours away and always feel reasonably fresh when arriving on site. My record was 5 1/2 hours to Hastings on the south coast and 7 1/2 hours to Newcastle when we had really heavy rain a couple of years back when the M1 was closed near Sheffield.