diff --git a/.gitignore b/.gitignore
index 8057dbb..b86fb2a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -12,6 +12,7 @@ venv/
 
 # App
 cache/
+config/local.py
 
 # Pytest
 .pytest_cache/
diff --git a/app.py b/app.py
index 2d2a2e2..04c2adc 100644
--- a/app.py
+++ b/app.py
@@ -3,6 +3,7 @@ Combine GWR Bristol→Paddington trains with Eurostar St Pancras→destination t
 """
 from flask import Flask, render_template, redirect, url_for, request
 from datetime import date, timedelta
+import os
 
 from cache import get_cached, set_cached
 import scraper.eurostar as eurostar_scraper
@@ -22,7 +23,16 @@ RTT_BRISTOL_URL = (
     "?stp=WVS&show=pax-calls&order=wtt"
 )
 
-app = Flask(__name__)
+app = Flask(__name__, instance_relative_config=False)
+app.config.from_object('config.default')
+_local = os.path.join(os.path.dirname(__file__), 'config', 'local.py')
+if os.path.exists(_local):
+    app.config.from_pyfile(_local)
+
+import cache
+import circle_line
+cache.CACHE_DIR = app.config['CACHE_DIR']
+circle_line._TXC_XML = app.config['CIRCLE_LINE_XML']
 
 DESTINATIONS = {
     'paris':      'Paris Gare du Nord',
diff --git a/cache.py b/cache.py
index 2e82500..31fad05 100644
--- a/cache.py
+++ b/cache.py
@@ -2,7 +2,7 @@ import json
 import os
 import time
 
-CACHE_DIR = os.path.join(os.path.dirname(__file__), 'cache')
+from config.default import CACHE_DIR  # overridden by app config after import
 
 
 def _cache_path(key: str) -> str:
diff --git a/circle_line.py b/circle_line.py
index 1fee867..5c942f9 100644
--- a/circle_line.py
+++ b/circle_line.py
@@ -11,7 +11,7 @@ from datetime import datetime, timedelta
 _PAD_STOP = '9400ZZLUPAH1'   # Paddington (H&C Line)
 _KXP_STOP = '9400ZZLUKSX3'   # King's Cross St Pancras
 
-_TXC_XML = os.path.join(os.path.dirname(__file__), 'output_txc_01CIR_.xml')
+from config.default import CIRCLE_LINE_XML as _TXC_XML  # overridden by app config after import
 _NS = {'t': 'http://www.transxchange.org.uk/'}
 
 # Populated on first call to next_service(); maps day-type -> sorted list of
diff --git a/config/__init__.py b/config/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/config/default.py b/config/default.py
new file mode 100644
index 0000000..aff1369
--- /dev/null
+++ b/config/default.py
@@ -0,0 +1,10 @@
+import os
+
+# Directory containing TfL reference data (TransXChange XML files etc.)
+TFL_DATA_DIR = os.path.expanduser('~/lib/data/tfl')
+
+# Directory for caching scraped train times
+CACHE_DIR = os.path.expanduser('~/lib/data/tfl/cache')
+
+# TransXChange timetable file for the Circle Line
+CIRCLE_LINE_XML = os.path.join(TFL_DATA_DIR, 'output_txc_01CIR_.xml')